Provided by: fetchmail_6.3.26-3ubuntu0.1~18.04.1_amd64 
NAME
fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server
SYNOPSIS
fetchmail [option...] [mailserver...]
fetchmailconf
DESCRIPTION
fetchmail is a mail-retrieval and forwarding utility; it fetches mail from remote
mailservers and forwards it to your local (client) machine's delivery system. You can
then handle the retrieved mail using normal mail user agents such as mutt(1), elm(1) or
Mail(1). The fetchmail utility can be run in a daemon mode to repeatedly poll one or more
systems at a specified interval.
The fetchmail program can gather mail from servers supporting any of the common mail-
retrieval protocols: POP2 (legacy, to be removed from future release), POP3, IMAP2bis,
IMAP4, and IMAP4rev1. It can also use the ESMTP ETRN extension and ODMR. (The RFCs
describing all these protocols are listed at the end of this manual page.)
While fetchmail is primarily intended to be used over on-demand TCP/IP links (such as SLIP
or PPP connections), it may also be useful as a message transfer agent for sites which
refuse for security reasons to permit (sender-initiated) SMTP transactions with sendmail.
SUPPORT, TROUBLESHOOTING
For troubleshooting, tracing and debugging, you need to increase fetchmail's verbosity to
actually see what happens. To do that, please run both of the two following commands,
adding all of the options you'd normally use.
env LC_ALL=C fetchmail -V -v --nodetach --nosyslog
(This command line prints in English how fetchmail understands your configuration.)
env LC_ALL=C fetchmail -vvv --nodetach --nosyslog
(This command line actually runs fetchmail with verbose English output.)
Also see item #G3 in fetchmail's FAQ ⟨http://fetchmail.berlios.de/fetchmail-FAQ.html#G3⟩
You can omit the LC_ALL=C part above if you want output in the local language (if
supported). However if you are posting to mailing lists, please leave it in. The
maintainers do not necessarily understand your language, please use English.
CONCEPTS
If fetchmail is used with a POP or an IMAP server (but not with ETRN or ODMR), it has two
fundamental modes of operation for each user account from which it retrieves mail:
singledrop- and multidrop-mode.
In singledrop-mode,
fetchmail assumes that all messages in the user's account (mailbox) are intended
for a single recipient. The identity of the recipient will either default to the
local user currently executing fetchmail, or will need to be explicitly specified
in the configuration file.
fetchmail uses singledrop-mode when the fetchmailrc configuration contains at most
a single local user specification for a given server account.
In multidrop-mode,
fetchmail assumes that the mail server account actually contains mail intended for
any number of different recipients. Therefore, fetchmail must attempt to deduce
the proper "envelope recipient" from the mail headers of each message. In this
mode of operation, fetchmail almost resembles a mail transfer agent (MTA).
Note that neither the POP nor IMAP protocols were intended for use in this fashion,
and hence envelope information is often not directly available. The ISP must
stores the envelope information in some message header and. The ISP must also store
one copy of the message per recipient. If either of the conditions is not
fulfilled, this process is unreliable, because fetchmail must then resort to
guessing the true envelope recipient(s) of a message. This usually fails for
mailing list messages and Bcc:d mail, or mail for multiple recipients in your
domain.
fetchmail uses multidrop-mode when more than one local user and/or a wildcard is
specified for a particular server account in the configuration file.
In ETRN and ODMR modes,
these considerations do not apply, as these protocols are based on SMTP, which
provides explicit envelope recipient information. These protocols always support
multiple recipients.
As each message is retrieved, fetchmail normally delivers it via SMTP to port 25 on the
machine it is running on (localhost), just as though it were being passed in over a normal
TCP/IP link. fetchmail provides the SMTP server with an envelope recipient derived in the
manner described previously. The mail will then be delivered according to your MTA's
rules (the Mail Transfer Agent is usually sendmail(8), exim(8), or postfix(8)). Invoking
your system's MDA (Mail Delivery Agent) is the duty of your MTA. All the delivery-control
mechanisms (such as .forward files) normally available through your system MTA and local
delivery agents will therefore be applied as usual.
If your fetchmail configuration sets a local MDA (see the --mda option), it will be used
directly instead of talking SMTP to port 25.
If the program fetchmailconf is available, it will assist you in setting up and editing a
fetchmailrc configuration. It runs under the X window system and requires that the
language Python and the Tk toolkit (with Python bindings) be present on your system. If
you are first setting up fetchmail for single-user mode, it is recommended that you use
Novice mode. Expert mode provides complete control of fetchmail configuration, including
the multidrop features. In either case, the 'Autoprobe' button will tell you the most
capable protocol a given mailserver supports, and warn you of potential problems with that
server.
GENERAL OPERATION
The behavior of fetchmail is controlled by command-line options and a run control file,
~/.fetchmailrc, the syntax of which we describe in a later section (this file is what the
fetchmailconf program edits). Command-line options override ~/.fetchmailrc declarations.
Each server name that you specify following the options on the command line will be
queried. If you don't specify any servers on the command line, each 'poll' entry in your
~/.fetchmailrc file will be queried.
To facilitate the use of fetchmail in scripts and pipelines, it returns an appropriate
exit code upon termination -- see EXIT CODES below.
The following options modify the behavior of fetchmail. It is seldom necessary to specify
any of these once you have a working .fetchmailrc file set up.
Almost all options have a corresponding keyword which can be used to declare them in a
.fetchmailrc file.
Some special options are not covered here, but are documented instead in sections on
AUTHENTICATION and DAEMON MODE which follow.
General Options
-V | --version
Displays the version information for your copy of fetchmail. No mail fetch is
performed. Instead, for each server specified, all the option information that
would be computed if fetchmail were connecting to that server is displayed. Any
non-printables in passwords or other string names are shown as backslashed C-like
escape sequences. This option is useful for verifying that your options are set
the way you want them.
-c | --check
Return a status code to indicate whether there is mail waiting, without actually
fetching or deleting mail (see EXIT CODES below). This option turns off daemon
mode (in which it would be useless). It doesn't play well with queries to multiple
sites, and doesn't work with ETRN or ODMR. It will return a false positive if you
leave read but undeleted mail in your server mailbox and your fetch protocol can't
tell kept messages from new ones. This means it will work with IMAP, not work with
POP2, and may occasionally flake out under POP3.
-s | --silent
Silent mode. Suppresses all progress/status messages that are normally echoed to
standard output during a fetch (but does not suppress actual error messages). The
--verbose option overrides this.
-v | --verbose
Verbose mode. All control messages passed between fetchmail and the mailserver are
echoed to stdout. Overrides --silent. Doubling this option (-v -v) causes extra
diagnostic information to be printed.
--nosoftbounce
(since v6.3.10, Keyword: set no softbounce, since v6.3.10)
Hard bounce mode. All permanent delivery errors cause messages to be deleted from
the upstream server, see "no softbounce" below.
--softbounce
(since v6.3.10, Keyword: set softbounce, since v6.3.10)
Soft bounce mode. All permanent delivery errors cause messages to be left on the
upstream server if the protocol supports that. This option is on by default to
match historic fetchmail documentation, and will be changed to hard bounce mode in
the next fetchmail release.
Disposal Options
-a | --all | (since v6.3.3) --fetchall
(Keyword: fetchall, since v3.0)
Retrieve both old (seen) and new messages from the mailserver. The default is to
fetch only messages the server has not marked seen. Under POP3, this option also
forces the use of RETR rather than TOP. Note that POP2 retrieval behaves as though
--all is always on (see RETRIEVAL FAILURE MODES below) and this option does not
work with ETRN or ODMR. While the -a and --all command-line and fetchall rcfile
options have been supported for a long time, the --fetchall command-line option was
added in v6.3.3.
-k | --keep
(Keyword: keep)
Keep retrieved messages on the remote mailserver. Normally, messages are deleted
from the folder on the mailserver after they have been retrieved. Specifying the
keep option causes retrieved messages to remain in your folder on the mailserver.
This option does not work with ETRN or ODMR. If used with POP3, it is recommended
to also specify the --uidl option or uidl keyword.
-K | --nokeep
(Keyword: nokeep)
Delete retrieved messages from the remote mailserver. This option forces retrieved
mail to be deleted. It may be useful if you have specified a default of keep in
your .fetchmailrc. This option is forced on with ETRN and ODMR.
-F | --flush
(Keyword: flush)
POP3/IMAP only. This is a dangerous option and can cause mail loss when used
improperly. It deletes old (seen) messages from the mailserver before retrieving
new messages. Warning: This can cause mail loss if you check your mail with other
clients than fetchmail, and cause fetchmail to delete a message it had never
fetched before. It can also cause mail loss if the mail server marks the message
seen after retrieval (IMAP2 servers). You should probably not use this option in
your configuration file. If you use it with POP3, you must use the 'uidl' option.
What you probably want is the default setting: if you don't specify '-k', then
fetchmail will automatically delete messages after successful delivery.
--limitflush
POP3/IMAP only, since version 6.3.0. Delete oversized messages from the mailserver
before retrieving new messages. The size limit should be separately specified with
the --limit option. This option does not work with ETRN or ODMR.
Protocol and Query Options
-p <proto> | --proto <proto> | --protocol <proto>
(Keyword: proto[col])
Specify the protocol to use when communicating with the remote mailserver. If no
protocol is specified, the default is AUTO. proto may be one of the following:
AUTO Tries IMAP, POP3, and POP2 (skipping any of these for which support has not
been compiled in).
POP2 Post Office Protocol 2 (legacy, to be removed from future release)
POP3 Post Office Protocol 3
APOP Use POP3 with old-fashioned MD5-challenge authentication. Considered not
resistant to man-in-the-middle attacks.
RPOP Use POP3 with RPOP authentication.
KPOP Use POP3 with Kerberos V4 authentication on port 1109.
SDPS Use POP3 with Demon Internet's SDPS extensions.
IMAP IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically detects their
capabilities).
ETRN Use the ESMTP ETRN option.
ODMR Use the the On-Demand Mail Relay ESMTP profile.
All these alternatives work in basically the same way (communicating with standard server
daemons to fetch mail already delivered to a mailbox on the server) except ETRN and ODMR.
The ETRN mode allows you to ask a compliant ESMTP server (such as BSD sendmail at release
8.8.0 or higher) to immediately open a sender-SMTP connection to your client machine and
begin forwarding any items addressed to your client machine in the server's queue of
undelivered mail. The ODMR mode requires an ODMR-capable server and works similarly to
ETRN, except that it does not require the client machine to have a static DNS.
-U | --uidl
(Keyword: uidl)
Force UIDL use (effective only with POP3). Force client-side tracking of 'newness'
of messages (UIDL stands for "unique ID listing" and is described in RFC1939). Use
with 'keep' to use a mailbox as a baby news drop for a group of users. The fact
that seen messages are skipped is logged, unless error logging is done through
syslog while running in daemon mode. Note that fetchmail may automatically enable
this option depending on upstream server capabilities. Note also that this option
may be removed and forced enabled in a future fetchmail version. See also:
--idfile.
--idle (since 6.3.3)
(Keyword: idle, since before 6.0.0)
Enable IDLE use (effective only with IMAP). Note that this works with only one
folder at a given time. While the idle rcfile keyword had been supported for a
long time, the --idle command-line option was added in version 6.3.3. IDLE use
means that fetchmail tells the IMAP server to send notice of new messages, so they
can be retrieved sooner than would be possible with regular polls.
-P <portnumber> | --service <servicename>
(Keyword: service) Since version 6.3.0.
The service option permits you to specify a service name to connect to. You can
specify a decimal port number here, if your services database lacks the required
service-port assignments. See the FAQ item R12 and the --ssl documentation for
details. This replaces the older --port option.
--port <portnumber>
(Keyword: port)
Obsolete version of --service that does not take service names. Note: this option
may be removed from a future version.
--principal <principal>
(Keyword: principal)
The principal option permits you to specify a service principal for mutual
authentication. This is applicable to POP3 or IMAP with Kerberos 4 authentication
only. It does not apply to Kerberos 5 or GSSAPI. This option may be removed in a
future fetchmail version.
-t <seconds> | --timeout <seconds>
(Keyword: timeout)
The timeout option allows you to set a server-nonresponse timeout in seconds. If a
mailserver does not send a greeting message or respond to commands for the given
number of seconds, fetchmail will drop the connection to it. Without such a
timeout fetchmail might hang until the TCP connection times out, trying to fetch
mail from a down host, which may be very long. This would be particularly annoying
for a fetchmail running in the background. There is a default timeout which
fetchmail -V will report. If a given connection receives too many timeouts in
succession, fetchmail will consider it wedged and stop retrying. The calling user
will be notified by email if this happens.
Beginning with fetchmail 6.3.10, the SMTP client uses the recommended minimum
timeouts from RFC-5321 while waiting for the SMTP/LMTP server it is talking to.
You can raise the timeouts even more, but you cannot shorten them. This is to avoid
a painful situation where fetchmail has been configured with a short timeout (a
minute or less), ships a long message (many MBytes) to the local MTA, which then
takes longer than timeout to respond "OK", which it eventually will; that would
mean the mail gets delivered properly, but fetchmail cannot notice it and will thus
refetch this big message over and over again.
--plugin <command>
(Keyword: plugin)
The plugin option allows you to use an external program to establish the TCP
connection. This is useful if you want to use ssh, or need some special
firewalling setup. The program will be looked up in $PATH and can optionally be
passed the hostname and port as arguments using "%h" and "%p" respectively (note
that the interpolation logic is rather primitive, and these tokens must be bounded
by whitespace or beginning of string or end of string). Fetchmail will write to
the plugin's stdin and read from the plugin's stdout.
--plugout <command>
(Keyword: plugout)
Identical to the plugin option above, but this one is used for the SMTP
connections.
-r <name> | --folder <name>
(Keyword: folder[s])
Causes a specified non-default mail folder on the mailserver (or comma-separated
list of folders) to be retrieved. The syntax of the folder name is server-
dependent. This option is not available under POP3, ETRN, or ODMR.
--tracepolls
(Keyword: tracepolls)
Tell fetchmail to poll trace information in the form 'polling account %s' and
'folder %s' to the Received line it generates, where the %s parts are replaced by
the user's remote name, the poll label, and the folder (mailbox) where available
(the Received header also normally includes the server's true name). This can be
used to facilitate mail filtering based on the account it is being received from.
The folder information is written only since version 6.3.4.
--ssl (Keyword: ssl)
Causes the connection to the mail server to be encrypted via SSL, by negotiating
SSL directly after connecting (SSL-wrapped mode). It is highly recommended to use
--sslcertck to validate the certificates presented by the server. Please see the
description of --sslproto below! More information is available in the README.SSL
file that ships with fetchmail.
Note that even if this option is omitted, fetchmail may still negotiate SSL in-band
for POP3 or IMAP, through the STLS or STARTTLS feature. You can use the --sslproto
option to modify that behavior.
If no port is specified, the connection is attempted to the well known port of the
SSL version of the base protocol. This is generally a different port than the port
used by the base protocol. For IMAP, this is port 143 for the clear protocol and
port 993 for the SSL secured protocol; for POP3, it is port 110 for the clear text
and port 995 for the encrypted variant.
If your system lacks the corresponding entries from /etc/services, see the
--service option and specify the numeric port number as given in the previous
paragraph (unless your ISP had directed you to different ports, which is uncommon
however).
--sslcert <name>
(Keyword: sslcert)
For certificate-based client authentication. Some SSL encrypted servers require
client side keys and certificates for authentication. In most cases, this is
optional. This specifies the location of the public key certificate to be
presented to the server at the time the SSL session is established. It is not
required (but may be provided) if the server does not require it. It may be the
same file as the private key (combined key and certificate file) but this is not
recommended. Also see --sslkey below.
NOTE: If you use client authentication, the user name is fetched from the
certificate's CommonName and overrides the name set with --user.
--sslkey <name>
(Keyword: sslkey)
Specifies the file name of the client side private SSL key. Some SSL encrypted
servers require client side keys and certificates for authentication. In most
cases, this is optional. This specifies the location of the private key used to
sign transactions with the server at the time the SSL session is established. It
is not required (but may be provided) if the server does not require it. It may be
the same file as the public key (combined key and certificate file) but this is not
recommended.
If a password is required to unlock the key, it will be prompted for at the time
just prior to establishing the session to the server. This can cause some
complications in daemon mode.
Also see --sslcert above.
--sslproto <value>
(Keyword: sslproto, NOTE: semantic changes since v6.4.0)
This option has a dual use, out of historic fetchmail behaviour. It controls both
the SSL/TLS protocol version and, if --ssl is not specified, the STARTTLS behaviour
(upgrading the protocol to an SSL or TLS connection in-band). Some other options
may however make TLS mandatory.
Only if this option and --ssl are both missing for a poll, there will be opportunistic TLS
for POP3 and IMAP, where fetchmail will attempt to upgrade to TLSv1 or newer.
Recognized values for --sslproto are given below. You should normally chose one of the
auto-negotiating options, i. e. 'auto' or one of the options ending in a plus (+)
character. Note that depending on OpenSSL library version and configuration, some options
cause run-time errors because the requested SSL or TLS versions are not supported by the
particular installed OpenSSL library.
'', the empty string
Disable STARTTLS. If --ssl is given for the same server, log an error and
pretend that 'auto' had been used instead.
'auto' (default). Since v6.4.0. Require TLS. Auto-negotiate TLSv1 or newer, disable
SSLv3 downgrade. (fetchmail 6.3.26 and older have auto-negotiated all
protocols that their OpenSSL library supported, including the broken SSLv3).
'SSL23'
see 'auto'.
'SSL3' Require SSLv3 exactly. SSLv3 is broken, not supported on all systems, avoid
it if possible. This will make fetchmail negotiate SSLv3 only, and is the
only way besides 'SSL3+' to have fetchmail 6.4.0 or newer permit SSLv3.
'SSL3+'
same as 'auto', but permit SSLv3 as well. This is the only way besides
'SSL3' to have fetchmail 6.4.0 or newer permit SSLv3.
'TLS1' Require TLSv1. This does not negotiate TLSv1.1 or newer, and is discouraged.
Replace by TLS1+ unless the latter chokes your server.
'TLS1+'
Since v6.4.0. See 'fBauto'.
'TLS1.1'
Since v6.4.0. Require TLS v1.1 exactly.
'TLS1.1+'
Since v6.4.0. Require TLS. Auto-negotiate TLSv1.1 or newer.
'TLS1.2'
Since v6.4.0. Require TLS v1.2 exactly.
'TLS1.2+'
Since v6.4.0. Require TLS. Auto-negotiate TLSv1.2 or newer.
Unrecognized parameters
are treated the same as 'auto'.
NOTE: you should hardly ever need to use anything other than '' (to force an
unencrypted connection) or 'auto' (to enforce TLS).
--sslcertck
(Keyword: sslcertck)
Causes fetchmail to require that SSL/TLS be used and disconnect if it can not
successfully negotiate SSL or TLS, or if it cannot successfully verify and validate
the certificate and follow it to a trust anchor (or trusted root certificate). The
trust anchors are given as a set of local trusted certificates (see the sslcertfile
and sslcertpath options). If the server certificate cannot be obtained or is not
signed by one of the trusted ones (directly or indirectly), fetchmail will
disconnect, regardless of the sslfingerprint option.
Note that CRL (certificate revocation lists) are only supported in OpenSSL 0.9.7
and newer! Your system clock should also be reasonably accurate when using this
option.
Note that this optional behavior may become default behavior in future fetchmail
versions.
--sslcertfile <file>
(Keyword: sslcertfile, since v6.3.17)
Sets the file fetchmail uses to look up local certificates. The default is empty.
This can be given in addition to --sslcertpath below, and certificates specified in
--sslcertfile will be processed before those in --sslcertpath. The option can be
used in addition to --sslcertpath.
The file is a text file. It contains the concatenation of trusted CA certificates
in PEM format.
Note that using this option will suppress loading the default SSL trusted CA
certificates file unless you set the environment variable
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.
--sslcertpath <directory>
(Keyword: sslcertpath)
Sets the directory fetchmail uses to look up local certificates. The default is
your OpenSSL default directory. The directory must be hashed the way OpenSSL
expects it - every time you add or modify a certificate in the directory, you need
to use the c_rehash tool (which comes with OpenSSL in the tools/ subdirectory).
Also, after OpenSSL upgrades, you may need to run c_rehash; particularly when
upgrading from 0.9.X to 1.0.0.
This can be given in addition to --sslcertfile above, which see for precedence
rules.
Note that using this option will suppress adding the default SSL trusted CA
certificates directory unless you set the environment variable
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.
--sslcommonname <common name>
(Keyword: sslcommonname; since v6.3.9)
Use of this option is discouraged. Before using it, contact the administrator of
your upstream server and ask for a proper SSL certificate to be used. If that
cannot be attained, this option can be used to specify the name (CommonName) that
fetchmail expects on the server certificate. A correctly configured server will
have this set to the hostname by which it is reached, and by default fetchmail will
expect as much. Use this option when the CommonName is set to some other value, to
avoid the "Server CommonName mismatch" warning, and only if the upstream server
can't be made to use proper certificates.
--sslfingerprint <fingerprint>
(Keyword: sslfingerprint)
Specify the fingerprint of the server key (an MD5 hash of the key) in hexadecimal
notation with colons separating groups of two digits. The letter hex digits must be
in upper case. This is the format that fetchmail uses to report the fingerprint
when an SSL connection is established. When this is specified, fetchmail will
compare the server key fingerprint with the given one, and the connection will fail
if they do not match, regardless of the sslcertck setting. The connection will also
fail if fetchmail cannot obtain an SSL certificate from the server. This can be
used to prevent man-in-the-middle attacks, but the finger print from the server
needs to be obtained or verified over a secure channel, and certainly not over the
same Internet connection that fetchmail would use.
Using this option will prevent printing certificate verification errors as long as
--sslcertck is unset.
To obtain the fingerprint of a certificate stored in the file cert.pem, try:
openssl x509 -in cert.pem -noout -md5 -fingerprint
For details, see x509(1ssl).
Delivery Control Options
-S <hosts> | --smtphost <hosts>
(Keyword: smtp[host])
Specify a hunt list of hosts to forward mail to (one or more hostnames, comma-
separated). Hosts are tried in list order; the first one that is up becomes the
forwarding target for the current run. If this option is not specified,
'localhost' is used as the default. Each hostname may have a port number following
the host name. The port number is separated from the host name by a slash; the
default port is "smtp". If you specify an absolute path name (beginning with a /),
it will be interpreted as the name of a UNIX socket accepting LMTP connections
(such as is supported by the Cyrus IMAP daemon) Example:
--smtphost server1,server2/2525,server3,/var/imap/socket/lmtp
This option can be used with ODMR, and will make fetchmail a relay between the ODMR
server and SMTP or LMTP receiver.
--fetchdomains <hosts>
(Keyword: fetchdomains)
In ETRN or ODMR mode, this option specifies the list of domains the server should
ship mail for once the connection is turned around. The default is the FQDN of the
machine running fetchmail.
-D <domain> | --smtpaddress <domain>
(Keyword: smtpaddress)
Specify the domain to be appended to addresses in RCPT TO lines shipped to SMTP.
When this is not specified, the name of the SMTP server (as specified by
--smtphost) is used for SMTP/LMTP and 'localhost' is used for UNIX socket/BSMTP.
--smtpname <user@domain>
(Keyword: smtpname)
Specify the domain and user to be put in RCPT TO lines shipped to SMTP. The
default user is the current local user.
-Z <nnn> | --antispam <nnn[, nnn]...>
(Keyword: antispam)
Specifies the list of numeric SMTP errors that are to be interpreted as a spam-
block response from the listener. A value of -1 disables this option. For the
command-line option, the list values should be comma-separated.
-m <command> | --mda <command>
(Keyword: mda)
This option lets fetchmail use a Message or Local Delivery Agent (MDA or LDA)
directly, rather than forward via SMTP or LMTP.
To avoid losing mail, use this option only with MDAs like maildrop or MTAs like
sendmail that exit with a nonzero status on disk-full and other delivery errors;
the nonzero status tells fetchmail that delivery failed and prevents the message
from being deleted on the server.
If fetchmail is running as root, it sets its user id while delivering mail through
an MDA as follows: First, the FETCHMAILUSER, LOGNAME, and USER environment
variables are checked in this order. The value of the first variable from his list
that is defined (even if it is empty!) is looked up in the system user database. If
none of the variables is defined, fetchmail will use the real user id it was
started with. If one of the variables was defined, but the user stated there isn't
found, fetchmail continues running as root, without checking remaining variables on
the list. Practically, this means that if you run fetchmail as root (not
recommended), it is most useful to define the FETCHMAILUSER environment variable to
set the user that the MDA should run as. Some MDAs (such as maildrop) are designed
to be setuid root and setuid to the recipient's user id, so you don't lose
functionality this way even when running fetchmail as unprivileged user. Check the
MDA's manual for details.
Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T" (Note: some several
older or vendor sendmail versions mistake -- for an address, rather than an
indicator to mark the end of the option arguments), "/usr/bin/deliver" and
"/usr/bin/maildrop -d %T". Local delivery addresses will be inserted into the MDA
command wherever you place a %T; the mail message's From address will be inserted
where you place an %F.
Do NOT enclose the %F or %T string in single quotes! For both %T and %F, fetchmail
encloses the addresses in single quotes ('), after removing any single quotes they
may contain, before the MDA command is passed to the shell.
Do NOT use an MDA invocation that dispatches on the contents of To/Cc/Bcc, like
"sendmail -i -t" or "qmail-inject", it will create mail loops and bring the just
wrath of many postmasters down upon your head. This is one of the most frequent
configuration errors!
Also, do not try to combine multidrop mode with an MDA such as maildrop that can
only accept one address, unless your upstream stores one copy of the message per
recipient and transports the envelope recipient in a header; you will lose mail.
The well-known procmail(1) package is very hard to configure properly, it has a
very nasty "fall through to the next rule" behavior on delivery errors (even
temporary ones, such as out of disk space if another user's mail daemon copies the
mailbox around to purge old messages), so your mail will end up in the wrong
mailbox sooner or later. The proper procmail configuration is outside the scope of
this document. Using maildrop(1) is usually much easier, and many users find the
filter syntax used by maildrop easier to understand.
Finally, we strongly advise that you do not use qmail-inject. The command line
interface is non-standard without providing benefits for typical use, and fetchmail
makes no attempts to accommodate qmail-inject's deviations from the standard. Some
of qmail-inject's command-line and environment options are actually dangerous and
can cause broken threads, non-detected duplicate messages and forwarding loops.
--lmtp (Keyword: lmtp)
Cause delivery via LMTP (Local Mail Transfer Protocol). A service host and port
must be explicitly specified on each host in the smtphost hunt list (see above) if
this option is selected; the default port 25 will (in accordance with RFC 2033) not
be accepted.
--bsmtp <filename>
(Keyword: bsmtp)
Append fetched mail to a BSMTP file. This simply contains the SMTP commands that
would normally be generated by fetchmail when passing mail to an SMTP listener
daemon.
An argument of '-' causes the SMTP batch to be written to standard output, which is
of limited use: this only makes sense for debugging, because fetchmail's regular
output is interspersed on the same channel, so this isn't suitable for mail
delivery. This special mode may be removed in a later release.
Note that fetchmail's reconstruction of MAIL FROM and RCPT TO lines is not
guaranteed correct; the caveats discussed under THE USE AND ABUSE OF MULTIDROP
MAILBOXES below apply. This mode has precedence before --mda and SMTP/LMTP.
--bad-header {reject|accept}
(Keyword: bad-header; since v6.3.15)
Specify how fetchmail is supposed to treat messages with bad headers, i. e. headers
with bad syntax. Traditionally, fetchmail has rejected such messages, but some
distributors modified fetchmail to accept them. You can now configure fetchmail's
behaviour per server.
Resource Limit Control Options
-l <maxbytes> | --limit <maxbytes>
(Keyword: limit)
Takes a maximum octet size argument, where 0 is the default and also the special
value designating "no limit". If nonzero, messages larger than this size will not
be fetched and will be left on the server (in foreground sessions, the progress
messages will note that they are "oversized"). If the fetch protocol permits (in
particular, under IMAP or POP3 without the fetchall option) the message will not be
marked seen.
An explicit --limit of 0 overrides any limits set in your run control file. This
option is intended for those needing to strictly control fetch time due to
expensive and variable phone rates.
Combined with --limitflush, it can be used to delete oversized messages waiting on
a server. In daemon mode, oversize notifications are mailed to the calling user
(see the --warnings option). This option does not work with ETRN or ODMR.
-w <interval> | --warnings <interval>
(Keyword: warnings)
Takes an interval in seconds. When you call fetchmail with a 'limit' option in
daemon mode, this controls the interval at which warnings about oversized messages
are mailed to the calling user (or the user specified by the 'postmaster' option).
One such notification is always mailed at the end of the the first poll that the
oversized message is detected. Thereafter, re-notification is suppressed until
after the warning interval elapses (it will take place at the end of the first
following poll).
-b <count> | --batchlimit <count>
(Keyword: batchlimit)
Specify the maximum number of messages that will be shipped to an SMTP listener
before the connection is deliberately torn down and rebuilt (defaults to 0, meaning
no limit). An explicit --batchlimit of 0 overrides any limits set in your run
control file. While sendmail(8) normally initiates delivery of a message
immediately after receiving the message terminator, some SMTP listeners are not so
prompt. MTAs like smail(8) may wait till the delivery socket is shut down to
deliver. This may produce annoying delays when fetchmail is processing very large
batches. Setting the batch limit to some nonzero size will prevent these delays.
This option does not work with ETRN or ODMR.
-B <number> | --fetchlimit <number>
(Keyword: fetchlimit)
Limit the number of messages accepted from a given server in a single poll. By
default there is no limit. An explicit --fetchlimit of 0 overrides any limits set
in your run control file. This option does not work with ETRN or ODMR.
--fetchsizelimit <number>
(Keyword: fetchsizelimit)
Limit the number of sizes of messages accepted from a given server in a single
transaction. This option is useful in reducing the delay in downloading the first
mail when there are too many mails in the mailbox. By default, the limit is 100.
If set to 0, sizes of all messages are downloaded at the start. This option does
not work with ETRN or ODMR. For POP3, the only valid non-zero value is 1.
--fastuidl <number>
(Keyword: fastuidl)
Do a binary instead of linear search for the first unseen UID. Binary search avoids
downloading the UIDs of all mails. This saves time (especially in daemon mode)
where downloading the same set of UIDs in each poll is a waste of bandwidth. The
number 'n' indicates how rarely a linear search should be done. In daemon mode,
linear search is used once followed by binary searches in 'n-1' polls if 'n' is
greater than 1; binary search is always used if 'n' is 1; linear search is always
used if 'n' is 0. In non-daemon mode, binary search is used if 'n' is 1; otherwise
linear search is used. The default value of 'n' is 4. This option works with POP3
only.
-e <count> | --expunge <count>
(Keyword: expunge)
Arrange for deletions to be made final after a given number of messages. Under
POP2 or POP3, fetchmail cannot make deletions final without sending QUIT and ending
the session -- with this option on, fetchmail will break a long mail retrieval
session into multiple sub-sessions, sending QUIT after each sub-session. This is a
good defense against line drops on POP3 servers. Under IMAP, fetchmail normally
issues an EXPUNGE command after each deletion in order to force the deletion to be
done immediately. This is safest when your connection to the server is flaky and
expensive, as it avoids resending duplicate mail after a line hit. However, on
large mailboxes the overhead of re-indexing after every message can slam the server
pretty hard, so if your connection is reliable it is good to do expunges less
frequently. Also note that some servers enforce a delay of a few seconds after
each quit, so fetchmail may not be able to get back in immediately after an expunge
-- you may see "lock busy" errors if this happens. If you specify this option to an
integer N, it tells fetchmail to only issue expunges on every Nth delete. An
argument of zero suppresses expunges entirely (so no expunges at all will be done
until the end of run). This option does not work with ETRN or ODMR.
Authentication Options
-u <name> | --user <name> | --username <name>
(Keyword: user[name])
Specifies the user identification to be used when logging in to the mailserver.
The appropriate user identification is both server and user-dependent. The default
is your login name on the client machine that is running fetchmail. See USER
AUTHENTICATION below for a complete description.
-I <specification> | --interface <specification>
(Keyword: interface)
Require that a specific interface device be up and have a specific local or remote
IPv4 (IPv6 is not supported by this option yet) address (or range) before polling.
Frequently fetchmail is used over a transient point-to-point TCP/IP link
established directly to a mailserver via SLIP or PPP. That is a relatively secure
channel. But when other TCP/IP routes to the mailserver exist (e.g. when the link
is connected to an alternate ISP), your username and password may be vulnerable to
snooping (especially when daemon mode automatically polls for mail, shipping a
clear password over the net at predictable intervals). The --interface option may
be used to prevent this. When the specified link is not up or is not connected to
a matching IP address, polling will be skipped. The format is:
interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]
The field before the first slash is the interface name (i.e. sl0, ppp0 etc.). The
field before the second slash is the acceptable IP address. The field after the
second slash is a mask which specifies a range of IP addresses to accept. If no
mask is present 255.255.255.255 is assumed (i.e. an exact match). This option is
currently only supported under Linux and FreeBSD. Please see the monitor section
for below for FreeBSD specific information.
Note that this option may be removed from a future fetchmail version.
-M <interface> | --monitor <interface>
(Keyword: monitor)
Daemon mode can cause transient links which are automatically taken down after a
period of inactivity (e.g. PPP links) to remain up indefinitely. This option
identifies a system TCP/IP interface to be monitored for activity. After each poll
interval, if the link is up but no other activity has occurred on the link, then
the poll will be skipped. However, when fetchmail is woken up by a signal, the
monitor check is skipped and the poll goes through unconditionally. This option is
currently only supported under Linux and FreeBSD. For the monitor and interface
options to work for non root users under FreeBSD, the fetchmail binary must be
installed SGID kmem. This would be a security hole, but fetchmail runs with the
effective GID set to that of the kmem group only when interface data is being
collected.
Note that this option may be removed from a future fetchmail version.
--auth <type>
(Keyword: auth[enticate])
This option permits you to specify an authentication type (see USER AUTHENTICATION
below for details). The possible values are any, password, kerberos_v5, kerberos
(or, for excruciating exactness, kerberos_v4), gssapi, cram-md5, otp, ntlm, msn
(only for POP3), external (only IMAP) and ssh. When any (the default) is
specified, fetchmail tries first methods that don't require a password (EXTERNAL,
GSSAPI, KERBEROS IV, KERBEROS 5); then it looks for methods that mask your password
(CRAM-MD5, NTLM, X-OTP - note that MSN is only supported for POP3, but not
autoprobed); and only if the server doesn't support any of those will it ship your
password en clair. Other values may be used to force various authentication
methods (ssh suppresses authentication and is thus useful for IMAP PREAUTH).
(external suppresses authentication and is thus useful for IMAP EXTERNAL). Any
value other than password, cram-md5, ntlm, msn or otp suppresses fetchmail's normal
inquiry for a password. Specify ssh when you are using an end-to-end secure
connection such as an ssh tunnel; specify external when you use TLS with client
authentication and specify gssapi or kerberos_v4 if you are using a protocol
variant that employs GSSAPI or K4. Choosing KPOP protocol automatically selects
Kerberos authentication. This option does not work with ETRN. GSSAPI service
names are in line with RFC-2743 and IANA registrations, see Generic Security
Service Application Program Interface (GSSAPI)/Kerberos/Simple Authentication and
Security Layer (SASL) Service Names ⟨http://www.iana.org/assignments/
gssapi-service-names/⟩.
Miscellaneous Options
-f <pathname> | --fetchmailrc <pathname>
Specify a non-default name for the ~/.fetchmailrc run control file. The pathname
argument must be either "-" (a single dash, meaning to read the configuration from
standard input) or a filename. Unless the --version option is also on, a named
file argument must have permissions no more open than 0700 (u=rwx,g=,o=) or else be
/dev/null.
-i <pathname> | --idfile <pathname>
(Keyword: idfile)
Specify an alternate name for the .fetchids file used to save message UIDs. NOTE:
since fetchmail 6.3.0, write access to the directory containing the idfile is
required, as fetchmail writes a temporary file and renames it into the place of the
real idfile only if the temporary file has been written successfully. This avoids
the truncation of idfiles when running out of disk space.
--pidfile <pathname>
(Keyword: pidfile; since fetchmail v6.3.4)
Override the default location of the PID file. Default: see "ENVIRONMENT" below.
-n | --norewrite
(Keyword: no rewrite)
Normally, fetchmail edits RFC-822 address headers (To, From, Cc, Bcc, and Reply-To)
in fetched mail so that any mail IDs local to the server are expanded to full
addresses (@ and the mailserver hostname are appended). This enables replies on
the client to get addressed correctly (otherwise your mailer might think they
should be addressed to local users on the client machine!). This option disables
the rewrite. (This option is provided to pacify people who are paranoid about
having an MTA edit mail headers and want to know they can prevent it, but it is
generally not a good idea to actually turn off rewrite.) When using ETRN or ODMR,
the rewrite option is ineffective.
-E <line> | --envelope <line>
(Keyword: envelope; Multidrop only)
In the configuration file, an enhanced syntax is used:
envelope [<count>] <line>
This option changes the header fetchmail assumes will carry a copy of the mail's
envelope address. Normally this is 'X-Envelope-To'. Other typically found headers
to carry envelope information are 'X-Original-To' and 'Delivered-To'. Now, since
these headers are not standardized, practice varies. See the discussion of
multidrop address handling below. As a special case, 'envelope "Received"' enables
parsing of sendmail-style Received lines. This is the default, but discouraged
because it is not fully reliable.
Note that fetchmail expects the Received-line to be in a specific format: It must
contain "by host for address", where host must match one of the mailserver names
that fetchmail recognizes for the account in question.
The optional count argument (only available in the configuration file) determines
how many header lines of this kind are skipped. A count of 1 means: skip the first,
take the second. A count of 2 means: skip the first and second, take the third, and
so on.
-Q <prefix> | --qvirtual <prefix>
(Keyword: qvirtual; Multidrop only)
The string prefix assigned to this option will be removed from the user name found
in the header specified with the envelope option (before doing multidrop name
mapping or localdomain checking, if either is applicable). This option is useful if
you are using fetchmail to collect the mail for an entire domain and your ISP (or
your mail redirection provider) is using qmail. One of the basic features of qmail
is the Delivered-To: message header. Whenever qmail delivers a message to a local
mailbox it puts the username and hostname of the envelope recipient on this line.
The major reason for this is to prevent mail loops. To set up qmail to batch mail
for a disconnected site the ISP-mailhost will have normally put that site in its
'Virtualhosts' control file so it will add a prefix to all mail addresses for this
site. This results in mail sent to 'username@userhost.userdom.dom.com' having a
Delivered-To: line of the form:
Delivered-To: mbox-userstr-username@userhost.example.com
The ISP can make the 'mbox-userstr-' prefix anything they choose but a string matching the
user host name is likely. By using the option 'envelope Delivered-To:' you can make
fetchmail reliably identify the original envelope recipient, but you have to strip the
'mbox-userstr-' prefix to deliver to the correct user. This is what this option is for.
--configdump
Parse the ~/.fetchmailrc file, interpret any command-line options specified, and
dump a configuration report to standard output. The configuration report is a data
structure assignment in the language Python. This option is meant to be used with
an interactive ~/.fetchmailrc editor like fetchmailconf, written in Python.
Removed Options
-T | --netsec
Removed before version 6.3.0, the required underlying inet6_apps library had been
discontinued and is no longer available.
USER AUTHENTICATION AND ENCRYPTION
All modes except ETRN require authentication of the client to the server. Normal user
authentication in fetchmail is very much like the authentication mechanism of ftp(1). The
correct user-id and password depend upon the underlying security system at the mailserver.
If the mailserver is a Unix machine on which you have an ordinary user account, your
regular login name and password are used with fetchmail. If you use the same login name
on both the server and the client machines, you needn't worry about specifying a user-id
with the -u option -- the default behavior is to use your login name on the client machine
as the user-id on the server machine. If you use a different login name on the server
machine, specify that login name with the -u option. e.g. if your login name is 'jsmith'
on a machine named 'mailgrunt', you would start fetchmail as follows:
fetchmail -u jsmith mailgrunt
The default behavior of fetchmail is to prompt you for your mailserver password before the
connection is established. This is the safest way to use fetchmail and ensures that your
password will not be compromised. You may also specify your password in your
~/.fetchmailrc file. This is convenient when using fetchmail in daemon mode or with
scripts.
Using netrc files
If you do not specify a password, and fetchmail cannot extract one from your
~/.fetchmailrc file, it will look for a ~/.netrc file in your home directory before
requesting one interactively; if an entry matching the mailserver is found in that file,
the password will be used. Fetchmail first looks for a match on poll name; if it finds
none, it checks for a match on via name. See the ftp(1) man page for details of the
syntax of the ~/.netrc file. To show a practical example, a .netrc might look like this:
machine hermes.example.org
login joe
password topsecret
You can repeat this block with different user information if you need to provide more than
one password.
This feature may allow you to avoid duplicating password information in more than one
file.
On mailservers that do not provide ordinary user accounts, your user-id and password are
usually assigned by the server administrator when you apply for a mailbox on the server.
Contact your server administrator if you don't know the correct user-id and password for
your mailbox account.
POP3 VARIANTS
Early versions of POP3 (RFC1081, RFC1225) supported a crude form of independent
authentication using the .rhosts file on the mailserver side. Under this RPOP variant, a
fixed per-user ID equivalent to a password was sent in clear over a link to a reserved
port, with the command RPOP rather than PASS to alert the server that it should do special
checking. RPOP is supported by fetchmail (you can specify 'protocol RPOP' to have the
program send 'RPOP' rather than 'PASS') but its use is strongly discouraged, and support
will be removed from a future fetchmail version. This facility was vulnerable to spoofing
and was withdrawn in RFC1460.
RFC1460 introduced APOP authentication. In this variant of POP3, you register an APOP
password on your server host (on some servers, the program to do this is called
popauth(8)). You put the same password in your ~/.fetchmailrc file. Each time fetchmail
logs in, it sends an MD5 hash of your password and the server greeting time to the server,
which can verify it by checking its authorization database.
Note that APOP is no longer considered resistant against man-in-the-middle attacks.
RETR or TOP
fetchmail makes some efforts to make the server believe messages had not been retrieved,
by using the TOP command with a large number of lines when possible. TOP is a command
that retrieves the full header and a fetchmail-specified amount of body lines. It is
optional and therefore not implemented by all servers, and some are known to implement it
improperly. On many servers however, the RETR command which retrieves the full message
with header and body, sets the "seen" flag (for instance, in a web interface), whereas the
TOP command does not do that.
fetchmail will always use the RETR command if "fetchall" is set. fetchmail will also use
the RETR command if "keep" is set and "uidl" is unset. Finally, fetchmail will use the
RETR command on Maillennium POP3/PROXY servers (used by Comcast) to avoid a deliberate TOP
misinterpretation in this server that causes message corruption.
In all other cases, fetchmail will use the TOP command. This implies that in "keep"
setups, "uidl" must be set if "TOP" is desired.
Note that this description is true for the current version of fetchmail, but the behavior
may change in future versions. In particular, fetchmail may prefer the RETR command
because the TOP command causes much grief on some servers and is only optional.
ALTERNATE AUTHENTICATION FORMS
If your fetchmail was built with Kerberos support and you specify Kerberos authentication
(either with --auth or the .fetchmailrc option authenticate kerberos_v4) it will try to
get a Kerberos ticket from the mailserver at the start of each query. Note: if either the
pollname or via name is 'hesiod', fetchmail will try to use Hesiod to look up the
mailserver.
If you use POP3 or IMAP with GSSAPI authentication, fetchmail will expect the server to
have RFC1731- or RFC1734-conforming GSSAPI capability, and will use it. Currently this
has only been tested over Kerberos V, so you're expected to already have a ticket-granting
ticket. You may pass a username different from your principal name using the standard
--user command or by the .fetchmailrc option user.
If your IMAP daemon returns the PREAUTH response in its greeting line, fetchmail will
notice this and skip the normal authentication step. This can be useful, e.g. if you
start imapd explicitly using ssh. In this case you can declare the authentication value
'ssh' on that site entry to stop .fetchmail from asking you for a password when it starts
up.
If you use client authentication with TLS1 and your IMAP daemon returns the AUTH=EXTERNAL
response, fetchmail will notice this and will use the authentication shortcut and will not
send the passphrase. In this case you can declare the authentication value 'external'
on that site to stop fetchmail from asking you for a password when it starts up.
If you are using POP3, and the server issues a one-time-password challenge conforming to
RFC1938, fetchmail will use your password as a pass phrase to generate the required
response. This avoids sending secrets over the net unencrypted.
Compuserve's RPA authentication is supported. If you compile in the support, fetchmail
will try to perform an RPA pass-phrase authentication instead of sending over the password
en clair if it detects "@compuserve.com" in the hostname.
If you are using IMAP, Microsoft's NTLM authentication (used by Microsoft Exchange) is
supported. If you compile in the support, fetchmail will try to perform an NTLM
authentication (instead of sending over the password en clair) whenever the server returns
AUTH=NTLM in its capability response. Specify a user option value that looks like
'user@domain': the part to the left of the @ will be passed as the username and the part
to the right as the NTLM domain.
Secure Socket Layers (SSL) and Transport Layer Security (TLS)
transport. Additionally, POP3 and IMAP retrival can also negotiate SSL/TLS by means of
STARTTLS (or STLS).
Note that fetchmail currently uses the OpenSSL library, which is severely underdocumented,
so failures may occur just because the programmers are not aware of OpenSSL's requirement
of the day. For instance, since v6.3.16, fetchmail calls OpenSSL_add_all_algorithms(),
which is necessary to support certificates using SHA256 on OpenSSL 0.9.8 -- this
information is deeply hidden in the documentation and not at all obvious. Please do not
hesitate to report subtle SSL failures.
You can access SSL encrypted services by specifying the options starting with --ssl, such
as --ssl, --sslproto, --sslcertck, and others. You can also do this using the
corresponding user options in the .fetchmailrc file. Some services, such as POP3 and
IMAP, have different well known ports defined for the SSL encrypted services. The
encrypted ports will be selected automatically when SSL is enabled and no explicit port is
specified. Also, the --sslcertck command line or sslcertck run control file option
should be used to force strict certificate checking - see below.
If SSL is not configured, fetchmail will usually opportunistically try to use STARTTLS.
STARTTLS can be enforced by using --sslproto auto and defeated by using --sslproto ''.
TLS connections use the same port as the unencrypted version of the protocol and negotiate
TLS via special command. The --sslcertck command line or sslcertck run control file option
should be used to force strict certificate checking - see below.
--sslcertck is recommended: When connecting to an SSL or TLS encrypted server, the server
presents a certificate to the client for validation. The certificate is checked to verify
that the common name in the certificate matches the name of the server being contacted and
that the effective and expiration dates in the certificate indicate that it is currently
valid. If any of these checks fail, a warning message is printed, but the connection
continues. The server certificate does not need to be signed by any specific Certifying
Authority and may be a "self-signed" certificate. If the --sslcertck command line option
or sslcertck run control file option is used, fetchmail will instead abort if any of these
checks fail, because it must assume that there is a man-in-the-middle attack in this
scenario, hence fetchmail must not expose cleartext passwords. Use of the sslcertck or
--sslcertck option is therefore advised.
Some SSL encrypted servers may request a client side certificate. A client side public
SSL certificate and private SSL key may be specified. If requested by the server, the
client certificate is sent to the server for validation. Some servers may require a valid
client certificate and may refuse connections if a certificate is not provided or if the
certificate is not valid. Some servers may require client side certificates be signed by
a recognized Certifying Authority. The format for the key files and the certificate files
is that required by the underlying SSL libraries (OpenSSL in the general case).
A word of care about the use of SSL: While above mentioned setup with self-signed server
certificates retrieved over the wires can protect you from a passive eavesdropper, it
doesn't help against an active attacker. It's clearly an improvement over sending the
passwords in clear, but you should be aware that a man-in-the-middle attack is trivially
possible (in particular with tools such as dsniff ⟨http://monkey.org/~dugsong/dsniff/⟩, ).
Use of strict certificate checking with a certification authority recognized by server and
client, or perhaps of an SSH tunnel (see below for some examples) is preferable if you
care seriously about the security of your mailbox and passwords.
ESMTP AUTH
fetchmail also supports authentication to the ESMTP server on the client side according to
RFC 2554. You can specify a name/password pair to be used with the keywords 'esmtpname'
and 'esmtppassword'; the former defaults to the username of the calling user.
DAEMON MODE
Introducing the daemon mode
In daemon mode, fetchmail puts itself into the background and runs forever, querying each
specified host and then sleeping for a given polling interval.
Starting the daemon mode
There are several ways to make fetchmail work in daemon mode. On the command line,
--daemon <interval> or -d <interval> option runs fetchmail in daemon mode. You must
specify a numeric argument which is a polling interval (time to wait after completing a
whole poll cycle with the last server and before starting the next poll cycle with the
first server) in seconds.
Example: simply invoking
fetchmail -d 900
will, therefore, poll all the hosts described in your ~/.fetchmailrc file (except those
explicitly excluded with the 'skip' verb) a bit less often than once every 15 minutes
(exactly: 15 minutes + time that the poll takes).
It is also possible to set a polling interval in your ~/.fetchmailrc file by saying
'set daemon <interval>', where <interval> is an integer number of seconds. If you do
this, fetchmail will always start in daemon mode unless you override it with the command-
line option --daemon 0 or -d0.
Only one daemon process is permitted per user; in daemon mode, fetchmail sets up a per-
user lockfile to guarantee this. (You can however cheat and set the FETCHMAILHOME
environment variable to overcome this setting, but in that case, it is your responsibility
to make sure you aren't polling the same server with two processes at the same time.)
Awakening the background daemon
Normally, calling fetchmail with a daemon in the background sends a wake-up signal to the
daemon and quits without output. The background daemon then starts its next poll cycle
immediately. The wake-up signal, SIGUSR1, can also be sent manually. The wake-up action
also clears any 'wedged' flags indicating that connections have wedged due to failed
authentication or multiple timeouts.
Terminating the background daemon
The option --quit will kill a running daemon process instead of waking it up (if there is
no such process, fetchmail will notify you). If the --quit option appears last on the
command line, fetchmail will kill the running daemon process and then quit. Otherwise,
fetchmail will first kill a running daemon process and then continue running with the
other options.
Useful options for daemon mode
The -L <filename> or --logfile <filename> option (keyword: set logfile) is only effective
when fetchmail is detached and in daemon mode. Note that the logfile must exist before
fetchmail is run, you can use the touch(1) command with the filename as its sole argument
to create it.
This option allows you to redirect status messages into a specified logfile (follow the
option with the logfile name). The logfile is opened for append, so previous messages
aren't deleted. This is primarily useful for debugging configurations. Note that
fetchmail does not detect if the logfile is rotated, the logfile is only opened once when
fetchmail starts. You need to restart fetchmail after rotating the logfile and before
compressing it (if applicable).
The --syslog option (keyword: set syslog) allows you to redirect status and error messages
emitted to the syslog(3) system daemon if available. Messages are logged with an id of
fetchmail, the facility LOG_MAIL, and priorities LOG_ERR, LOG_ALERT or LOG_INFO. This
option is intended for logging status and error messages which indicate the status of the
daemon and the results while fetching mail from the server(s). Error messages for command
line options and parsing the .fetchmailrc file are still written to stderr, or to the
specified log file. The --nosyslog option turns off use of syslog(3), assuming it's
turned on in the ~/.fetchmailrc file. This option is overridden, in certain situations,
by --logfile (which see).
The -N or --nodetach option suppresses backgrounding and detachment of the daemon process
from its control terminal. This is useful for debugging or when fetchmail runs as the
child of a supervisor process such as init(8) or Gerrit Pape's runit(8). Note that this
also causes the logfile option to be ignored.
Note that while running in daemon mode polling a POP2 or IMAP2bis server, transient errors
(such as DNS failures or sendmail delivery refusals) may force the fetchall option on for
the duration of the next polling cycle. This is a robustness feature. It means that if a
message is fetched (and thus marked seen by the mailserver) but not delivered locally due
to some transient error, it will be re-fetched during the next poll cycle. (The IMAP
logic doesn't delete messages until they're delivered, so this problem does not arise.)
If you touch or change the ~/.fetchmailrc file while fetchmail is running in daemon mode,
this will be detected at the beginning of the next poll cycle. When a changed
~/.fetchmailrc is detected, fetchmail rereads it and restarts from scratch (using exec(2);
no state information is retained in the new instance). Note that if fetchmail needs to
query for passwords, of that if you break the ~/.fetchmailrc file's syntax, the new
instance will softly and silently vanish away on startup.
ADMINISTRATIVE OPTIONS
The --postmaster <name> option (keyword: set postmaster) specifies the last-resort
username to which multidrop mail is to be forwarded if no matching local recipient can be
found. It is also used as destination of undeliverable mail if the 'bouncemail' global
option is off and additionally for spam-blocked mail if the 'bouncemail' global option is
off and the 'spambounce' global option is on. This option defaults to the user who invoked
fetchmail. If the invoking user is root, then the default of this option is the user
'postmaster'. Setting postmaster to the empty string causes such mail as described above
to be discarded - this however is usually a bad idea. See also the description of the
'FETCHMAILUSER' environment variable in the ENVIRONMENT section below.
The --nobounce behaves like the "set no bouncemail" global option, which see.
The --invisible option (keyword: set invisible) tries to make fetchmail invisible.
Normally, fetchmail behaves like any other MTA would -- it generates a Received header
into each message describing its place in the chain of transmission, and tells the MTA it
forwards to that the mail came from the machine fetchmail itself is running on. If the
invisible option is on, the Received header is suppressed and fetchmail tries to spoof the
MTA it forwards to into thinking it came directly from the mailserver host.
The --showdots option (keyword: set showdots) forces fetchmail to show progress dots even
if the output goes to a file or fetchmail is not in verbose mode. Fetchmail shows the
dots by default when run in --verbose mode and output goes to console. This option is
ignored in --silent mode.
By specifying the --tracepolls option, you can ask fetchmail to add information to the
Received header on the form "polling {label} account {user}", where {label} is the account
label (from the specified rcfile, normally ~/.fetchmailrc) and {user} is the username
which is used to log on to the mail server. This header can be used to make filtering
email where no useful header information is available and you want mail from different
accounts sorted into different mailboxes (this could, for example, occur if you have an
account on the same server running a mailing list, and are subscribed to the list using
that account). The default is not adding any such header. In .fetchmailrc, this is called
'tracepolls'.
RETRIEVAL FAILURE MODES
The protocols fetchmail uses to talk to mailservers are next to bulletproof. In normal
operation forwarding to port 25, no message is ever deleted (or even marked for deletion)
on the host until the SMTP listener on the client side has acknowledged to fetchmail that
the message has been either accepted for delivery or rejected due to a spam block.
When forwarding to an MDA, however, there is more possibility of error. Some MDAs are
'safe' and reliably return a nonzero status on any delivery error, even one due to
temporary resource limits. The maildrop(1) program is like this; so are most programs
designed as mail transport agents, such as sendmail(1), including the sendmail wrapper of
Postfix and exim(1). These programs give back a reliable positive acknowledgement and can
be used with the mda option with no risk of mail loss. Unsafe MDAs, though, may return 0
even on delivery failure. If this happens, you will lose mail.
The normal mode of fetchmail is to try to download only 'new' messages, leaving untouched
(and undeleted) messages you have already read directly on the server (or fetched with a
previous fetchmail --keep). But you may find that messages you've already read on the
server are being fetched (and deleted) even when you don't specify --all. There are
several reasons this can happen.
One could be that you're using POP2. The POP2 protocol includes no representation of
'new' or 'old' state in messages, so fetchmail must treat all messages as new all the
time. But POP2 is obsolete, so this is unlikely.
A potential POP3 problem might be servers that insert messages in the middle of mailboxes
(some VMS implementations of mail are rumored to do this). The fetchmail code assumes
that new messages are appended to the end of the mailbox; when this is not true it may
treat some old messages as new and vice versa. Using UIDL whilst setting fastuidl 0 might
fix this, otherwise, consider switching to IMAP.
Yet another POP3 problem is that if they can't make tempfiles in the user's home
directory, some POP3 servers will hand back an undocumented response that causes fetchmail
to spuriously report "No mail".
The IMAP code uses the presence or absence of the server flag \Seen to decide whether or
not a message is new. This isn't the right thing to do, fetchmail should check the
UIDVALIDITY and use UID, but it doesn't do that yet. Under Unix, it counts on your IMAP
server to notice the BSD-style Status flags set by mail user agents and set the \Seen flag
from them when appropriate. All Unix IMAP servers we know of do this, though it's not
specified by the IMAP RFCs. If you ever trip over a server that doesn't, the symptom will
be that messages you have already read on your host will look new to the server. In this
(unlikely) case, only messages you fetched with fetchmail --keep will be both undeleted
and marked old.
In ETRN and ODMR modes, fetchmail does not actually retrieve messages; instead, it asks
the server's SMTP listener to start a queue flush to the client via SMTP. Therefore it
sends only undelivered messages.
SPAM FILTERING
Many SMTP listeners allow administrators to set up 'spam filters' that block unsolicited
email from specified domains. A MAIL FROM or DATA line that triggers this feature will
elicit an SMTP response which (unfortunately) varies according to the listener.
Newer versions of sendmail return an error code of 571.
According to RFC2821, the correct thing to return in this situation is 550 "Requested
action not taken: mailbox unavailable" (the draft adds "[E.g., mailbox not found, no
access, or command rejected for policy reasons].").
Older versions of the exim MTA return 501 "Syntax error in parameters or arguments".
The postfix MTA runs 554 as an antispam response.
Zmailer may reject code with a 500 response (followed by an enhanced status code that
contains more information).
Return codes which fetchmail treats as antispam responses and discards the message can be
set with the 'antispam' option. This is one of the only three circumstance under which
fetchmail ever discards mail (the others are the 552 and 553 errors described below, and
the suppression of multidropped messages with a message-ID already seen).
If fetchmail is fetching from an IMAP server, the antispam response will be detected and
the message rejected immediately after the headers have been fetched, without reading the
message body. Thus, you won't pay for downloading spam message bodies.
By default, the list of antispam responses is empty.
If the spambounce global option is on, mail that is spam-blocked triggers an
RFC1892/RFC1894 bounce message informing the originator that we do not accept mail from
it. See also BUGS.
SMTP/ESMTP ERROR HANDLING
Besides the spam-blocking described above, fetchmail takes special actions — that may be
modified by the --softbounce option — on the following SMTP/ESMTP error response codes
452 (insufficient system storage)
Leave the message in the server mailbox for later retrieval.
552 (message exceeds fixed maximum message size)
Delete the message from the server. Send bounce-mail to the originator.
553 (invalid sending domain)
Delete the message from the server. Don't even try to send bounce-mail to the
originator.
Other errors greater or equal to 500 trigger bounce mail back to the originator, unless
suppressed by --softbounce. See also BUGS.
THE RUN CONTROL FILE
The preferred way to set up fetchmail is to write a .fetchmailrc file in your home
directory (you may do this directly, with a text editor, or indirectly via fetchmailconf).
When there is a conflict between the command-line arguments and the arguments in this
file, the command-line arguments take precedence.
To protect the security of your passwords, your ~/.fetchmailrc may not normally have more
than 0700 (u=rwx,g=,o=) permissions; fetchmail will complain and exit otherwise (this
check is suppressed when --version is on).
You may read the .fetchmailrc file as a list of commands to be executed when fetchmail is
called with no arguments.
Run Control Syntax
Comments begin with a '#' and extend through the end of the line. Otherwise the file
consists of a series of server entries or global option statements in a free-format,
token-oriented syntax.
There are four kinds of tokens: grammar keywords, numbers (i.e. decimal digit sequences),
unquoted strings, and quoted strings. A quoted string is bounded by double quotes and may
contain whitespace (and quoted digits are treated as a string). Note that quoted strings
will also contain line feed characters if they run across two or more lines, unless you
use a backslash to join lines (see below). An unquoted string is any whitespace-delimited
token that is neither numeric, string quoted nor contains the special characters ',', ';',
':', or '='.
Any amount of whitespace separates tokens in server entries, but is otherwise ignored. You
may use backslash escape sequences (\n for LF, \t for HT, \b for BS, \r for CR, \nnn for
decimal (where nnn cannot start with a 0), \0ooo for octal, and \xhh for hex) to embed
non-printable characters or string delimiters in strings. In quoted strings, a backslash
at the very end of a line will cause the backslash itself and the line feed (LF or NL, new
line) character to be ignored, so that you can wrap long strings. Without the backslash at
the line end, the line feed character would become part of the string.
Warning: while these resemble C-style escape sequences, they are not the same. fetchmail
only supports these eight styles. C supports more escape sequences that consist of
backslash (\) and a single character, but does not support decimal codes and does not
require the leading 0 in octal notation. Example: fetchmail interprets \233 the same as
\xE9 (Latin small letter e with acute), where C would interpret \233 as octal 0233 = \x9B
(CSI, control sequence introducer).
Each server entry consists of one of the keywords 'poll' or 'skip', followed by a server
name, followed by server options, followed by any number of user (or username)
descriptions, followed by user options. Note: the most common cause of syntax errors is
mixing up user and server options or putting user options before the user descriptions.
For backward compatibility, the word 'server' is a synonym for 'poll'.
You can use the noise keywords 'and', 'with', 'has', 'wants', and 'options' anywhere in an
entry to make it resemble English. They're ignored, but but can make entries much easier
to read at a glance. The punctuation characters ':', ';' and ',' are also ignored.
Poll vs. Skip
The 'poll' verb tells fetchmail to query this host when it is run with no arguments. The
'skip' verb tells fetchmail not to poll this host unless it is explicitly named on the
command line. (The 'skip' verb allows you to experiment with test entries safely, or
easily disable entries for hosts that are temporarily down.)
Keyword/Option Summary
Here are the legal options. Keyword suffixes enclosed in square brackets are optional.
Those corresponding to short command-line options are followed by '-' and the appropriate
option letter. If option is only relevant to a single mode of operation, it is noted as
's' or 'm' for singledrop- or multidrop-mode, respectively.
Here are the legal global options:
Keyword Opt Mode Function
────────────────────────────────────────────────────────────────────
set daemon -d Set a background poll interval in
seconds.
set postmaster Give the name of the last-resort
mail recipient (default: user
running fetchmail, "postmaster" if
run by the root user)
set bouncemail Direct error mail to the sender
(default)
set no bouncemail Direct error mail to the local
postmaster (as per the
'postmaster' global option above).
set no spambounce Do not bounce spam-blocked mail
(default).
set spambounce Bounce blocked spam-blocked mail
(as per the 'antispam' user
option) back to the destination as
indicated by the 'bouncemail'
global option. Warning: Do not
use this to bounce spam back to
the sender - most spam is sent
with false sender address and thus
this option hurts innocent
bystanders.
set no softbounce Delete permanently undeliverable
mail. It is recommended to use
this option if the configuration
has been thoroughly tested.
set softbounce Keep permanently undeliverable
mail as though a temporary error
had occurred (default).
set logfile -L Name of a file to append error and
status messages to. Only
effective in daemon mode and if
fetchmail detaches. If effective,
overrides set syslog.
set idfile -i Name of the file to store UID
lists in.
set syslog Do error logging through
syslog(3). May be overriden by set
logfile.
set no syslog Turn off error logging through
syslog(3). (default)
set properties String value that is ignored by
fetchmail (may be used by
extension scripts).
Here are the legal server options:
Keyword Opt Mode Function
─────────────────────────────────────────────────────────────────
via Specify DNS name of mailserver,
overriding poll name
proto[col] -p Specify protocol (case
insensitive): POP2, POP3, IMAP,
APOP, KPOP
local[domains] m Specify domain(s) to be regarded
as local
port Specify TCP/IP service port
(obsolete, use 'service' instead).
service -P Specify service name (a numeric
value is also allowed and
considered a TCP/IP port number).
auth[enticate] Set authentication type (default
'any')
timeout -t Server inactivity timeout in
seconds (default 300)
envelope -E m Specify envelope-address header
name
no envelope m Disable looking for envelope
address
qvirtual -Q m Qmail virtual domain prefix to
remove from user name
aka m Specify alternate DNS names of
mailserver
interface -I specify IP interface(s) that must
be up for server poll to take
place
monitor -M Specify IP address to monitor for
activity
plugin Specify command through which to
make server connections.
plugout Specify command through which to
make listener connections.
dns m Enable DNS lookup for multidrop
(default)
no dns m Disable DNS lookup for multidrop
checkalias m Do comparison by IP address for
multidrop
no checkalias m Do comparison by name for
multidrop (default)
uidl -U Force POP3 to use client-side
UIDLs (recommended)
no uidl Turn off POP3 use of client-side
UIDLs (default)
interval Only check this site every N poll
cycles; N is a numeric argument.
tracepolls Add poll tracing information to
the Received header
principal Set Kerberos principal (only
useful with IMAP and kerberos)
esmtpname Set name for RFC2554
authentication to the ESMTP
server.
esmtppassword Set password for RFC2554
authentication to the ESMTP
server.
bad-header How to treat messages with a bad
header. Can be reject (default) or
accept.
Here are the legal user descriptions and options:
Keyword Opt Mode Function
───────────────────────────────────────────────────────────────────
user[name] -u This is the user description and
must come first after server
description and after possible
server options, and before user
options.
It sets the remote user name if by
itself or followed by 'there', or
the local user name if followed by
'here'.
is Connect local and remote user
names
to Connect local and remote user
names
pass[word] Specify remote account password
ssl Connect to server over the
specified base protocol using SSL
encryption
sslcert Specify file for client side
public SSL certificate
sslcertfile Specify file with trusted CA
certificates
sslcertpath Specify c_rehash-ed directory with
trusted CA certificates.
sslkey Specify file for client side
private SSL key
sslproto Force ssl protocol for connection
folder -r Specify remote folder to query
smtphost -S Specify smtp host(s) to forward to
fetchdomains m Specify domains for which mail
should be fetched
smtpaddress -D Specify the domain to be put in
RCPT TO lines
smtpname Specify the user and domain to be
put in RCPT TO lines
antispam -Z Specify what SMTP returns are
interpreted as spam-policy blocks
mda -m Specify MDA for local delivery
bsmtp -o Specify BSMTP batch file to append
to
preconnect Command to be executed before each
connection
postconnect Command to be executed after each
connection
keep -k Don't delete seen messages from
server (for POP3, uidl is
recommended)
flush -F Flush all seen messages before
querying (DANGEROUS)
limitflush Flush all oversized messages
before querying
fetchall -a Fetch all messages whether seen or
not
rewrite Rewrite destination addresses for
reply (default)
stripcr Strip carriage returns from ends
of lines
forcecr Force carriage returns at ends of
lines
pass8bits Force BODY=8BITMIME to ESMTP
listener
dropstatus Strip Status and X-Mozilla-Status
lines out of incoming mail
dropdelivered Strip Delivered-To lines out of
incoming mail
mimedecode Convert quoted-printable to 8-bit
in MIME messages
idle Idle waiting for new messages
after each poll (IMAP only)
no keep -K Delete seen messages from server
(default)
no flush Don't flush all seen messages
before querying (default)
no fetchall Retrieve only new messages
(default)
no rewrite Don't rewrite headers
no stripcr Don't strip carriage returns
(default)
no forcecr Don't force carriage returns at
EOL (default)
no pass8bits Don't force BODY=8BITMIME to ESMTP
listener (default)
no dropstatus Don't drop Status headers
(default)
no dropdelivered Don't drop Delivered-To headers
(default)
no mimedecode Don't convert quoted-printable to
8-bit in MIME messages (default)
no idle Don't idle waiting for new
messages after each poll (IMAP
only)
limit -l Set message size limit
warnings -w Set message size warning interval
batchlimit -b Max # messages to forward in
single connect
fetchlimit -B Max # messages to fetch in single
connect
fetchsizelimit Max # message sizes to fetch in
single transaction
fastuidl Use binary search for first unseen
message (POP3 only)
expunge -e Perform an expunge on every #th
message (IMAP and POP3 only)
properties String value is ignored by
fetchmail (may be used by
extension scripts)
All user options must begin with a user description (user or username option) and follow
all server descriptions and options.
In the .fetchmailrc file, the 'envelope' string argument may be preceded by a whitespace-
separated number. This number, if specified, is the number of such headers to skip over
(that is, an argument of 1 selects the second header of the given type). This is sometime
useful for ignoring bogus envelope headers created by an ISP's local delivery agent or
internal forwards (through mail inspection systems, for instance).
Keywords Not Corresponding To Option Switches
The 'folder' and 'smtphost' options (unlike their command-line equivalents) can take a
space- or comma-separated list of names following them.
All options correspond to the obvious command-line arguments, except the following: 'via',
'interval', 'aka', 'is', 'to', 'dns'/'no dns', 'checkalias'/'no checkalias', 'password',
'preconnect', 'postconnect', 'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no
forcecr', 'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus', 'dropdelivered/no
dropdelivered', 'mimedecode/no mimedecode', 'no idle', and 'no envelope'.
The 'via' option is for if you want to have more than one configuration pointing at the
same site. If it is present, the string argument will be taken as the actual DNS name of
the mailserver host to query. This will override the argument of poll, which can then
simply be a distinct label for the configuration (e.g. what you would give on the command
line to explicitly query this host).
The 'interval' option (which takes a numeric argument) allows you to poll a server less
frequently than the basic poll interval. If you say 'interval N' the server this option
is attached to will only be queried every N poll intervals.
Singledrop vs. Multidrop options
Please ensure you read the section titled THE USE AND ABUSE OF MULTIDROP MAILBOXES if you
intend to use multidrop mode.
The 'is' or 'to' keywords associate the following local (client) name(s) (or server-name
to client-name mappings separated by =) with the mailserver user name in the entry. If an
is/to list has '*' as its last name, unrecognized names are simply passed through. Note
that until fetchmail version 6.3.4 inclusively, these lists could only contain local parts
of user names (fetchmail would only look at the part before the @ sign). fetchmail
versions 6.3.5 and newer support full addresses on the left hand side of these mappings,
and they take precedence over any 'localdomains', 'aka', 'via' or similar mappings.
A single local name can be used to support redirecting your mail when your username on the
client machine is different from your name on the mailserver. When there is only a single
local name, mail is forwarded to that local username regardless of the message's Received,
To, Cc, and Bcc headers. In this case, fetchmail never does DNS lookups.
When there is more than one local name (or name mapping), fetchmail looks at the envelope
header, if configured, and otherwise at the Received, To, Cc, and Bcc headers of retrieved
mail (this is 'multidrop mode'). It looks for addresses with hostname parts that match
your poll name or your 'via', 'aka' or 'localdomains' options, and usually also for
hostname parts which DNS tells it are aliases of the mailserver. See the discussion of
'dns', 'checkalias', 'localdomains', and 'aka' for details on how matching addresses are
handled.
If fetchmail cannot match any mailserver usernames or localdomain addresses, the mail will
be bounced. Normally it will be bounced to the sender, but if the 'bouncemail' global
option is off, the mail will go to the local postmaster instead. (see the 'postmaster'
global option). See also BUGS.
The 'dns' option (normally on) controls the way addresses from multidrop mailboxes are
checked. On, it enables logic to check each host address that does not match an 'aka' or
'localdomains' declaration by looking it up with DNS. When a mailserver username is
recognized attached to a matching hostname part, its local mapping is added to the list of
local recipients.
The 'checkalias' option (normally off) extends the lookups performed by the 'dns' keyword
in multidrop mode, providing a way to cope with remote MTAs that identify themselves using
their canonical name, while they're polled using an alias. When such a server is polled,
checks to extract the envelope address fail, and fetchmail reverts to delivery using the
To/Cc/Bcc headers (See below 'Header vs. Envelope addresses'). Specifying this option
instructs fetchmail to retrieve all the IP addresses associated with both the poll name
and the name used by the remote MTA and to do a comparison of the IP addresses. This
comes in handy in situations where the remote server undergoes frequent canonical name
changes, that would otherwise require modifications to the rcfile. 'checkalias' has no
effect if 'no dns' is specified in the rcfile.
The 'aka' option is for use with multidrop mailboxes. It allows you to pre-declare a list
of DNS aliases for a server. This is an optimization hack that allows you to trade space
for speed. When fetchmail, while processing a multidrop mailbox, grovels through message
headers looking for names of the mailserver, pre-declaring common ones can save it from
having to do DNS lookups. Note: the names you give as arguments to 'aka' are matched as
suffixes -- if you specify (say) 'aka netaxs.com', this will match not just a hostname
netaxs.com, but any hostname that ends with '.netaxs.com'; such as (say) pop3.netaxs.com
and mail.netaxs.com.
The 'localdomains' option allows you to declare a list of domains which fetchmail should
consider local. When fetchmail is parsing address lines in multidrop modes, and a
trailing segment of a host name matches a declared local domain, that address is passed
through to the listener or MDA unaltered (local-name mappings are not applied).
If you are using 'localdomains', you may also need to specify 'no envelope', which
disables fetchmail's normal attempt to deduce an envelope address from the Received line
or X-Envelope-To header or whatever header has been previously set by 'envelope'. If you
set 'no envelope' in the defaults entry it is possible to undo that in individual entries
by using 'envelope <string>'. As a special case, 'envelope "Received"' restores the
default parsing of Received lines.
The password option requires a string argument, which is the password to be used with the
entry's server.
The 'preconnect' keyword allows you to specify a shell command to be executed just before
each time fetchmail establishes a mailserver connection. This may be useful if you are
attempting to set up secure POP connections with the aid of ssh(1). If the command
returns a nonzero status, the poll of that mailserver will be aborted.
Similarly, the 'postconnect' keyword similarly allows you to specify a shell command to be
executed just after each time a mailserver connection is taken down.
The 'forcecr' option controls whether lines terminated by LF only are given CRLF
termination before forwarding. Strictly speaking RFC821 requires this, but few MTAs
enforce the requirement it so this option is normally off (only one such MTA, qmail, is in
significant use at time of writing).
The 'stripcr' option controls whether carriage returns are stripped out of retrieved mail
before it is forwarded. It is normally not necessary to set this, because it defaults to
'on' (CR stripping enabled) when there is an MDA declared but 'off' (CR stripping
disabled) when forwarding is via SMTP. If 'stripcr' and 'forcecr' are both on, 'stripcr'
will override.
The 'pass8bits' option exists to cope with Microsoft mail programs that stupidly slap a
"Content-Transfer-Encoding: 7bit" on everything. With this option off (the default) and
such a header present, fetchmail declares BODY=7BIT to an ESMTP-capable listener; this
causes problems for messages actually using 8-bit ISO or KOI-8 character sets, which will
be garbled by having the high bits of all characters stripped. If 'pass8bits' is on,
fetchmail is forced to declare BODY=8BITMIME to any ESMTP-capable listener. If the
listener is 8-bit-clean (as all the major ones now are) the right thing will probably
result.
The 'dropstatus' option controls whether nonempty Status and X-Mozilla-Status lines are
retained in fetched mail (the default) or discarded. Retaining them allows your MUA to
see what messages (if any) were marked seen on the server. On the other hand, it can
confuse some new-mail notifiers, which assume that anything with a Status line in it has
been seen. (Note: the empty Status lines inserted by some buggy POP servers are
unconditionally discarded.)
The 'dropdelivered' option controls whether Delivered-To headers will be kept in fetched
mail (the default) or discarded. These headers are added by Qmail and Postfix mailservers
in order to avoid mail loops but may get in your way if you try to "mirror" a mailserver
within the same domain. Use with caution.
The 'mimedecode' option controls whether MIME messages using the quoted-printable encoding
are automatically converted into pure 8-bit data. If you are delivering mail to an ESMTP-
capable, 8-bit-clean listener (that includes all of the major MTAs like sendmail), then
this will automatically convert quoted-printable message headers and data into 8-bit data,
making it easier to understand when reading mail. If your e-mail programs know how to deal
with MIME messages, then this option is not needed. The mimedecode option is off by
default, because doing RFC2047 conversion on headers throws away character-set information
and can lead to bad results if the encoding of the headers differs from the body encoding.
The 'idle' option is intended to be used with IMAP servers supporting the RFC2177 IDLE
command extension, but does not strictly require it. If it is enabled, and fetchmail
detects that IDLE is supported, an IDLE will be issued at the end of each poll. This will
tell the IMAP server to hold the connection open and notify the client when new mail is
available. If IDLE is not supported, fetchmail will simulate it by periodically issuing
NOOP. If you need to poll a link frequently, IDLE can save bandwidth by eliminating TCP/IP
connects and LOGIN/LOGOUT sequences. On the other hand, an IDLE connection will eat almost
all of your fetchmail's time, because it will never drop the connection and allow other
polls to occur unless the server times out the IDLE. It also doesn't work with multiple
folders; only the first folder will ever be polled.
The 'properties' option is an extension mechanism. It takes a string argument, which is
ignored by fetchmail itself. The string argument may be used to store configuration
information for scripts which require it. In particular, the output of '--configdump'
option will make properties associated with a user entry readily available to a Python
script.
Miscellaneous Run Control Options
The words 'here' and 'there' have useful English-like significance. Normally 'user eric
is esr' would mean that mail for the remote user 'eric' is to be delivered to 'esr', but
you can make this clearer by saying 'user eric there is esr here', or reverse it by saying
'user esr here is eric there'
Legal protocol identifiers for use with the 'protocol' keyword are:
auto (or AUTO) (legacy, to be removed from future release)
pop2 (or POP2) (legacy, to be removed from future release)
pop3 (or POP3)
sdps (or SDPS)
imap (or IMAP)
apop (or APOP)
kpop (or KPOP)
Legal authentication types are 'any', 'password', 'kerberos', 'kerberos_v4', 'kerberos_v5'
and 'gssapi', 'cram-md5', 'otp', 'msn' (only for POP3), 'ntlm', 'ssh', 'external' (only
IMAP). The 'password' type specifies authentication by normal transmission of a password
(the password may be plain text or subject to protocol-specific encryption as in CRAM-
MD5); 'kerberos' tells fetchmail to try to get a Kerberos ticket at the start of each
query instead, and send an arbitrary string as the password; and 'gssapi' tells fetchmail
to use GSSAPI authentication. See the description of the 'auth' keyword for more.
Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4 authentication.
These defaults may be overridden by later options.
There are some global option statements: 'set logfile' followed by a string sets the same
global specified by --logfile. A command-line --logfile option will override this. Note
that --logfile is only effective if fetchmail detaches itself from the terminal and the
logfile already exists before fetchmail is run, and it overrides --syslog in this case.
Also, 'set daemon' sets the poll interval as --daemon does. This can be overridden by a
command-line --daemon option; in particular --daemon 0 can be used to force foreground
operation. The 'set postmaster' statement sets the address to which multidrop mail
defaults if there are no local matches. Finally, 'set syslog' sends log messages to
syslogd(8).
DEBUGGING FETCHMAIL
Fetchmail crashing
There are various ways in that fetchmail may "crash", i. e. stop operation suddenly and
unexpectedly. A "crash" usually refers to an error condition that the software did not
handle by itself. A well-known failure mode is the "segmentation fault" or "signal 11" or
"SIGSEGV" or just "segfault" for short. These can be caused by hardware or by software
problems. Software-induced segfaults can usually be reproduced easily and in the same
place, whereas hardware-induced segfaults can go away if the computer is rebooted, or
powered off for a few hours, and can happen in random locations even if you use the
software the same way.
For solving hardware-induced segfaults, find the faulty component and repair or replace
it. The Sig11 FAQ ⟨http://www.bitwizard.nl/sig11/⟩ may help you with details.
For solving software-induced segfaults, the developers may need a "stack backtrace".
Enabling fetchmail core dumps
By default, fetchmail suppresses core dumps as these might contain passwords and other
sensitive information. For debugging fetchmail crashes, obtaining a "stack backtrace" from
a core dump is often the quickest way to solve the problem, and when posting your problem
on a mailing list, the developers may ask you for a "backtrace".
1. To get useful backtraces, fetchmail needs to be installed without getting stripped of
its compilation symbols. Unfortunately, most binary packages that are installed are
stripped, and core files from symbol-stripped programs are worthless. So you may need to
recompile fetchmail. On many systems, you can type
file `which fetchmail`
to find out if fetchmail was symbol-stripped or not. If yours was unstripped, fine,
proceed, if it was stripped, you need to recompile the source code first. You do not
usually need to install fetchmail in order to debug it.
2. The shell environment that starts fetchmail needs to enable core dumps. The key is the
"maximum core (file) size" that can usually be configured with a tool named "limit" or
"ulimit". See the documentation for your shell for details. In the popular bash shell,
"ulimit -Sc unlimited" will allow the core dump.
3. You need to tell fetchmail, too, to allow core dumps. To do this, run fetchmail with
the -d0 -v options. It is often easier to also add --nosyslog -N as well.
Finally, you need to reproduce the crash. You can just start fetchmail from the directory
where you compiled it by typing ./fetchmail, so the complete command line will start with
./fetchmail -Nvd0 --nosyslog and perhaps list your other options.
After the crash, run your debugger to obtain the core dump. The debugger will often be
GNU GDB, you can then type (adjust paths as necessary) gdb ./fetchmail fetchmail.core and
then, after GDB has started up and read all its files, type backtrace full, save the
output (copy & paste will do, the backtrace will be read by a human) and then type quit to
leave gdb. Note: on some systems, the core files have different names, they might contain
a number instead of the program name, or number and name, but it will usually have "core"
as part of their name.
INTERACTION WITH RFC 822
When trying to determine the originating address of a message, fetchmail looks through
headers in the following order:
Return-Path:
Resent-Sender: (ignored if it doesn't contain an @ or !)
Sender: (ignored if it doesn't contain an @ or !)
Resent-From:
From:
Reply-To:
Apparently-From:
The originating address is used for logging, and to set the MAIL FROM address when
forwarding to SMTP. This order is intended to cope gracefully with receiving mailing list
messages in multidrop mode. The intent is that if a local address doesn't exist, the
bounce message won't be returned blindly to the author or to the list itself, but rather
to the list manager (which is less annoying).
In multidrop mode, destination headers are processed as follows: First, fetchmail looks
for the header specified by the 'envelope' option in order to determine the local
recipient address. If the mail is addressed to more than one recipient, the Received line
won't contain any information regarding recipient addresses.
Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc: lines. If they
exist, they should contain the final recipients and have precedence over their
To:/Cc:/Bcc: counterparts. If the Resent-* lines don't exist, the To:, Cc:, Bcc: and
Apparently-To: lines are looked for. (The presence of a Resent-To: is taken to imply that
the person referred by the To: address has already received the original copy of the
mail.)
CONFIGURATION EXAMPLES
Note that although there are password declarations in a good many of the examples below,
this is mainly for illustrative purposes. We recommend stashing account/password pairs in
your $HOME/.netrc file, where they can be used not just by fetchmail but by ftp(1) and
other programs.
The basic format is:
poll SERVERNAME protocol PROTOCOL username NAME password PASSWORD
Example:
poll pop.provider.net protocol pop3 username "jsmith" password "secret1"
Or, using some abbreviations:
poll pop.provider.net proto pop3 user "jsmith" password "secret1"
Multiple servers may be listed:
poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"
Here's the same version with more whitespace and some noise words:
poll pop.provider.net proto pop3
user "jsmith", with password secret1, is "jsmith" here;
poll other.provider.net proto pop2:
user "John.Smith", with password "My^Hat", is "John.Smith" here;
If you need to include whitespace in a parameter string or start the latter with a number,
enclose the string in double quotes. Thus:
poll mail.provider.net with proto pop3:
user "jsmith" there has password "4u but u can't krak this"
is jws here and wants mda "/bin/mail"
You may have an initial server description headed by the keyword 'defaults' instead of
'poll' followed by a name. Such a record is interpreted as defaults for all queries to
use. It may be overwritten by individual server descriptions. So, you could write:
defaults proto pop3
user "jsmith"
poll pop.provider.net
pass "secret1"
poll mail.provider.net
user "jjsmith" there has password "secret2"
It's possible to specify more than one user per server. The 'user' keyword leads off a
user description, and every user specification in a multi-user entry must include it.
Here's an example:
poll pop.provider.net proto pop3 port 3111
user "jsmith" with pass "secret1" is "smith" here
user jones with pass "secret2" is "jjones" here keep
This associates the local username 'smith' with the pop.provider.net username 'jsmith' and
the local username 'jjones' with the pop.provider.net username 'jones'. Mail for 'jones'
is kept on the server after download.
Here's what a simple retrieval configuration for a multidrop mailbox looks like:
poll pop.provider.net:
user maildrop with pass secret1 to golux 'hurkle'='happy' snark here
This says that the mailbox of account 'maildrop' on the server is a multidrop box, and
that messages in it should be parsed for the server user names 'golux', 'hurkle', and
'snark'. It further specifies that 'golux' and 'snark' have the same name on the client
as on the server, but mail for server user 'hurkle' should be delivered to client user
'happy'.
Note that fetchmail, until version 6.3.4, did NOT allow full user@domain specifications
here, these would never match. Fetchmail 6.3.5 and newer support user@domain
specifications on the left-hand side of a user mapping.
Here's an example of another kind of multidrop connection:
poll pop.provider.net localdomains loonytoons.org toons.org
envelope X-Envelope-To
user maildrop with pass secret1 to * here
This also says that the mailbox of account 'maildrop' on the server is a multidrop box.
It tells fetchmail that any address in the loonytoons.org or toons.org domains (including
sub-domain addresses like 'joe@daffy.loonytoons.org') should be passed through to the
local SMTP listener without modification. Be careful of mail loops if you do this!
Here's an example configuration using ssh and the plugin option. The queries are made
directly on the stdin and stdout of imapd via ssh. Note that in this setup, IMAP
authentication can be skipped.
poll mailhost.net with proto imap:
plugin "ssh %h /usr/sbin/imapd" auth ssh;
user esr is esr here
THE USE AND ABUSE OF MULTIDROP MAILBOXES
Use the multiple-local-recipients feature with caution -- it can bite. All multidrop
features are ineffective in ETRN and ODMR modes.
Also, note that in multidrop mode duplicate mails are suppressed. A piece of mail is
considered duplicate if it has the same message-ID as the message immediately preceding
and more than one addressee. Such runs of messages may be generated when copies of a
message addressed to multiple users are delivered to a multidrop box.
Header vs. Envelope addresses
The fundamental problem is that by having your mailserver toss several peoples' mail in a
single maildrop box, you may have thrown away potentially vital information about who each
piece of mail was actually addressed to (the 'envelope address', as opposed to the header
addresses in the RFC822 To/Cc headers - the Bcc is not available at the receiving end).
This 'envelope address' is the address you need in order to reroute mail properly.
Sometimes fetchmail can deduce the envelope address. If the mailserver MTA is sendmail
and the item of mail had just one recipient, the MTA will have written a 'by/for' clause
that gives the envelope addressee into its Received header. But this doesn't work reliably
for other MTAs, nor if there is more than one recipient. By default, fetchmail looks for
envelope addresses in these lines; you can restore this default with -E "Received" or
'envelope Received'.
As a better alternative, some SMTP listeners and/or mail servers insert a header in each
message containing a copy of the envelope addresses. This header (when it exists) is
often 'X-Original-To', 'Delivered-To' or 'X-Envelope-To'. Fetchmail's assumption about
this can be changed with the -E or 'envelope' option. Note that writing an envelope
header of this kind exposes the names of recipients (including blind-copy recipients) to
all receivers of the messages, so the upstream must store one copy of the message per
recipient to avoid becoming a privacy problem.
Postfix, since version 2.0, writes an X-Original-To: header which contains a copy of the
envelope as it was received.
Qmail and Postfix generally write a 'Delivered-To' header upon delivering the message to
the mail spool and use it to avoid mail loops. Qmail virtual domains however will prefix
the user name with a string that normally matches the user's domain. To remove this prefix
you can use the -Q or 'qvirtual' option.
Sometimes, unfortunately, neither of these methods works. That is the point when you
should contact your ISP and ask them to provide such an envelope header, and you should
not use multidrop in this situation. When they all fail, fetchmail must fall back on the
contents of To/Cc headers (Bcc headers are not available - see below) to try to determine
recipient addressees -- and these are unreliable. In particular, mailing-list software
often ships mail with only the list broadcast address in the To header.
Note that a future version of fetchmail may remove To/Cc parsing!
When fetchmail cannot deduce a recipient address that is local, and the intended recipient
address was anyone other than fetchmail's invoking user, mail will get lost. This is what
makes the multidrop feature risky without proper envelope information.
A related problem is that when you blind-copy a mail message, the Bcc information is
carried only as envelope address (it's removed from the headers by the sending mail
server, so fetchmail can see it only if there is an X-Envelope-To header). Thus, blind-
copying to someone who gets mail over a fetchmail multidrop link will fail unless the the
mailserver host routinely writes X-Envelope-To or an equivalent header into messages in
your maildrop.
In conclusion, mailing lists and Bcc'd mail can only work if the server you're fetching
from
(1) stores one copy of the message per recipient in your domain and
(2) records the envelope information in a special header (X-Original-To, Delivered-To,
X-Envelope-To).
Good Ways To Use Multidrop Mailboxes
Multiple local names can be used to administer a mailing list from the client side of a
fetchmail collection. Suppose your name is 'esr', and you want to both pick up your own
mail and maintain a mailing list called (say) "fetchmail-friends", and you want to keep
the alias list on your client machine.
On your server, you can alias 'fetchmail-friends' to 'esr'; then, in your .fetchmailrc,
declare 'to esr fetchmail-friends here'. Then, when mail including 'fetchmail-friends' as
a local address gets fetched, the list name will be appended to the list of recipients
your SMTP listener sees. Therefore it will undergo alias expansion locally. Be sure to
include 'esr' in the local alias expansion of fetchmail-friends, or you'll never see mail
sent only to the list. Also be sure that your listener has the "me-too" option set
(sendmail's -oXm command-line option or OXm declaration) so your name isn't removed from
alias expansions in messages you send.
This trick is not without its problems, however. You'll begin to see this when a message
comes in that is addressed only to a mailing list you do not have declared as a local
name. Each such message will feature an 'X-Fetchmail-Warning' header which is generated
because fetchmail cannot find a valid local name in the recipient addresses. Such
messages default (as was described above) to being sent to the local user running
fetchmail, but the program has no way to know that that's actually the right thing.
Bad Ways To Abuse Multidrop Mailboxes
Multidrop mailboxes and fetchmail serving multiple users in daemon mode do not mix. The
problem, again, is mail from mailing lists, which typically does not have an individual
recipient address on it. Unless fetchmail can deduce an envelope address, such mail will
only go to the account running fetchmail (probably root). Also, blind-copied users are
very likely never to see their mail at all.
If you're tempted to use fetchmail to retrieve mail for multiple users from a single mail
drop via POP or IMAP, think again (and reread the section on header and envelope addresses
above). It would be smarter to just let the mail sit in the mailserver's queue and use
fetchmail's ETRN or ODMR modes to trigger SMTP sends periodically (of course, this means
you have to poll more frequently than the mailserver's expiry period). If you can't
arrange this, try setting up a UUCP feed.
If you absolutely must use multidrop for this purpose, make sure your mailserver writes an
envelope-address header that fetchmail can see. Otherwise you will lose mail and it will
come back to haunt you.
Speeding Up Multidrop Checking
Normally, when multiple users are declared fetchmail extracts recipient addresses as
described above and checks each host part with DNS to see if it's an alias of the
mailserver. If so, the name mappings described in the "to ... here" declaration are done
and the mail locally delivered.
This is a convenient but also slow method. To speed it up, pre-declare mailserver aliases
with 'aka'; these are checked before DNS lookups are done. If you're certain your aka
list contains all DNS aliases of the mailserver (and all MX names pointing at it - note
this may change in a future version) you can declare 'no dns' to suppress DNS lookups
entirely and only match against the aka list.
SOCKS
Support for socks4/5 is a compile time configuration option. Once compiled in, fetchmail
will always use the socks libraries and configuration on your system, there are no run-
time switches in fetchmail - but you can still configure SOCKS: you can specify which
SOCKS configuration file is used in the SOCKS_CONF environment variable.
For instance, if you wanted to bypass the SOCKS proxy altogether and have fetchmail
connect directly, you could just pass SOCKS_CONF=/dev/null in the environment, for example
(add your usual command line options - if any - to the end of this line):
env SOCKS_CONF=/dev/null fetchmail
EXIT CODES
To facilitate the use of fetchmail in shell scripts, an exit status code is returned to
give an indication of what occurred during a given connection.
The exit codes returned by fetchmail are as follows:
0 One or more messages were successfully retrieved (or, if the -c option was
selected, were found waiting but not retrieved).
1 There was no mail awaiting retrieval. (There may have been old mail still on the
server but not selected for retrieval.) If you do not want "no mail" to be an error
condition (for instance, for cron jobs), use a POSIX-compliant shell and add
|| [ $? -eq 1 ]
to the end of the fetchmail command line, note that this leaves 0 untouched, maps 1
to 0, and maps all other codes to 1. See also item #C8 in the FAQ.
2 An error was encountered when attempting to open a socket to retrieve mail. If you
don't know what a socket is, don't worry about it -- just treat this as an
'unrecoverable error'. This error can also be because a protocol fetchmail wants
to use is not listed in /etc/services.
3 The user authentication step failed. This usually means that a bad user-id,
password, or APOP id was specified. Or it may mean that you tried to run fetchmail
under circumstances where it did not have standard input attached to a terminal and
could not prompt for a missing password.
4 Some sort of fatal protocol error was detected.
5 There was a syntax error in the arguments to fetchmail, or a pre- or post-connect
command failed.
6 The run control file had bad permissions.
7 There was an error condition reported by the server. Can also fire if fetchmail
timed out while waiting for the server.
8 Client-side exclusion error. This means fetchmail either found another copy of
itself already running, or failed in such a way that it isn't sure whether another
copy is running.
9 The user authentication step failed because the server responded "lock busy". Try
again after a brief pause! This error is not implemented for all protocols, nor
for all servers. If not implemented for your server, "3" will be returned instead,
see above. May be returned when talking to qpopper or other servers that can
respond with "lock busy" or some similar text containing the word "lock".
10 The fetchmail run failed while trying to do an SMTP port open or transaction.
11 Fatal DNS error. Fetchmail encountered an error while performing a DNS lookup at
startup and could not proceed.
12 BSMTP batch file could not be opened.
13 Poll terminated by a fetch limit (see the --fetchlimit option).
14 Server busy indication.
23 Internal error. You should see a message on standard error with details.
24 - 26, 28, 29
These are internal codes and should not appear externally.
When fetchmail queries more than one host, return status is 0 if any query successfully
retrieved mail. Otherwise the returned error status is that of the last host queried.
FILES
~/.fetchmailrc
default run control file
~/.fetchids
default location of file recording last message UIDs seen per host.
~/.fetchmail.pid
lock file to help prevent concurrent runs (non-root mode).
~/.netrc
your FTP run control file, which (if present) will be searched for passwords as a
last resort before prompting for one interactively.
/var/run/fetchmail.pid
lock file to help prevent concurrent runs (root mode, Linux systems).
/etc/fetchmail.pid
lock file to help prevent concurrent runs (root mode, systems without /var/run).
ENVIRONMENT
FETCHMAILHOME
If this environment variable is set to a valid and existing directory name,
fetchmail will read $FETCHMAILHOME/fetchmailrc (the dot is missing in this case),
$FETCHMAILHOME/.fetchids and $FETCHMAILHOME/.fetchmail.pid rather than from the
user's home directory. The .netrc file is always looked for in the the invoking
user's home directory regardless of FETCHMAILHOME's setting.
FETCHMAILUSER
If this environment variable is set, it is used as the name of the calling user
(default local name) for purposes such as mailing error notifications. Otherwise,
if either the LOGNAME or USER variable is correctly set (e.g. the corresponding UID
matches the session user ID) then that name is used as the default local name.
Otherwise getpwuid(3) must be able to retrieve a password entry for the session ID
(this elaborate logic is designed to handle the case of multiple names per userid
gracefully).
FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE
(since v6.3.22): If this environment variable is set and not empty, fetchmail will
disable a countermeasure against an SSL CBC IV attack (by setting
SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS). This is a security risk, but may be necessary
for connecting to certain non-standards-conforming servers. See fetchmail's NEWS
file and fetchmail-SA-2012-01.txt for details. Earlier fetchmail versions (v6.3.21
and older) used to disable this countermeasure, but v6.3.22 no longer does that as
a safety precaution.
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS
(since v6.3.17): If this environment variable is set and not empty, fetchmail will
always load the default X.509 trusted certificate locations for SSL/TLS CA
certificates, even if --sslcertfile and --sslcertpath are given. The latter
locations take precedence over the system default locations. This is useful in
case there are broken certificates in the system directories and the user has no
administrator privileges to remedy the problem.
HOME_ETC
If the HOME_ETC variable is set, fetchmail will read $HOME_ETC/.fetchmailrc instead
of ~/.fetchmailrc.
If HOME_ETC and FETCHMAILHOME are both set, HOME_ETC will be ignored.
SOCKS_CONF
(only if SOCKS support is compiled in) this variable is used by the socks library
to find out which configuration file it should read. Set this to /dev/null to
bypass the SOCKS proxy.
SIGNALS
If a fetchmail daemon is running as root, SIGUSR1 wakes it up from its sleep phase and
forces a poll of all non-skipped servers. For compatibility reasons, SIGHUP can also be
used in 6.3.X but may not be available in future fetchmail versions.
If fetchmail is running in daemon mode as non-root, use SIGUSR1 to wake it (this is so
SIGHUP due to logout can retain the default action of killing it).
Running fetchmail in foreground while a background fetchmail is running will do whichever
of these is appropriate to wake it up.
BUGS, LIMITATIONS, AND KNOWN PROBLEMS
Please check the NEWS file that shipped with fetchmail for more known bugs than those
listed here.
Fetchmail cannot handle user names that contain blanks after a "@" character, for instance
"demonstr@ti on". These are rather uncommon and only hurt when using UID-based --keep
setups, so the 6.3.X versions of fetchmail won't be fixed.
Fetchmail cannot handle configurations where you have multiple accounts that use the same
server name and the same login. Any user@server combination must be unique.
The assumptions that the DNS and in particular the checkalias options make are not often
sustainable. For instance, it has become uncommon for an MX server to be a POP3 or IMAP
server at the same time. Therefore the MX lookups may go away in a future release.
The mda and plugin options interact badly. In order to collect error status from the MDA,
fetchmail has to change its normal signal handling so that dead plugin processes don't get
reaped until the end of the poll cycle. This can cause resource starvation if too many
zombies accumulate. So either don't deliver to a MDA using plugins or risk being overrun
by an army of undead.
The --interface option does not support IPv6 and it is doubtful if it ever will, since
there is no portable way to query interface IPv6 addresses.
The RFC822 address parser used in multidrop mode chokes on some @-addresses that are
technically legal but bizarre. Strange uses of quoting and embedded comments are likely
to confuse it.
In a message with multiple envelope headers, only the last one processed will be visible
to fetchmail.
Use of some of these protocols requires that the program send unencrypted passwords over
the TCP/IP connection to the mailserver. This creates a risk that name/password pairs
might be snaffled with a packet sniffer or more sophisticated monitoring software. Under
Linux and FreeBSD, the --interface option can be used to restrict polling to availability
of a specific interface device with a specific local or remote IP address, but snooping is
still possible if (a) either host has a network device that can be opened in promiscuous
mode, or (b) the intervening network link can be tapped. We recommend the use of ssh(1)
tunnelling to not only shroud your passwords but encrypt the entire conversation.
Use of the %F or %T escapes in an mda option could open a security hole, because they pass
text manipulable by an attacker to a shell command. Potential shell characters are
replaced by '_' before execution. The hole is further reduced by the fact that fetchmail
temporarily discards any suid privileges it may have while running the MDA. For maximum
safety, however, don't use an mda command containing %F or %T when fetchmail is run from
the root account itself.
Fetchmail's method of sending bounces due to errors or spam-blocking and spam bounces
requires that port 25 of localhost be available for sending mail via SMTP.
If you modify ~/.fetchmailrc while a background instance is running and break the syntax,
the background instance will die silently. Unfortunately, it can't die noisily because we
don't yet know whether syslog should be enabled. On some systems, fetchmail dies quietly
even if there is no syntax error; this seems to have something to do with buggy terminal
ioctl code in the kernel.
The -f - option (reading a configuration from stdin) is incompatible with the plugin
option.
The 'principal' option only handles Kerberos IV, not V.
Interactively entered passwords are truncated after 63 characters. If you really need to
use a longer password, you will have to use a configuration file.
A backslash as the last character of a configuration file will be flagged as a syntax
error rather than ignored.
The BSMTP error handling is virtually nonexistent and may leave broken messages behind.
Send comments, bug reports, gripes, and the like to the fetchmail-devel list
⟨fetchmail-devel@lists.berlios.de⟩
An HTML FAQ ⟨http://fetchmail.berlios.de/fetchmail-FAQ.html⟩ is available at the fetchmail
home page, it should also accompany your installation.
AUTHOR
Fetchmail is currently maintained by Matthias Andree and Rob Funk with major assistance
from Sunil Shetye (for code) and Rob MacGregor (for the mailing lists).
Most of the code is from Eric S. Raymond ⟨esr@snark.thyrsus.com⟩ . Too many other people
to name here have contributed code and patches.
This program is descended from and replaces popclient, by Carl Harris ⟨ceharris@mal.com⟩ ;
the internals have become quite different, but some of its interface design is directly
traceable to that ancestral program.
This manual page has been improved by Matthias Andree, R. Hannes Beinert, and Héctor
García.
SEE ALSO
README, README.SSL, README.SSL-SERVER, The Fetchmail FAQ ⟨http://www.fetchmail.info/
fetchmail-FAQ.html⟩, mutt(1), elm(1), mail(1), sendmail(8), popd(8), imapd(8), netrc(5).
The fetchmail home page. ⟨http://fetchmail.berlios.de/⟩
The maildrop home page. ⟨http://www.courier-mta.org/maildrop/⟩
APPLICABLE STANDARDS
Note that this list is just a collection of references and not a statement as to the
actual protocol conformance or requirements in fetchmail.
SMTP/ESMTP:
RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC 1985, RFC 2554.
mail:
RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.
POP2:
RFC 937
POP3:
RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC 1957, RFC 2195, RFC
2449.
APOP:
RFC 1939.
RPOP:
RFC 1081, RFC 1225.
IMAP2/IMAP2BIS:
RFC 1176, RFC 1732.
IMAP4/IMAP4rev1:
RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC 2177, RFC 2683.
ETRN:
RFC 1985.
ODMR/ATRN:
RFC 2645.
OTP: RFC 1938.
LMTP:
RFC 2033.
GSSAPI:
RFC 1508, RFC 1734, Generic Security Service Application Program Interface
(GSSAPI)/Kerberos/Simple Authentication and Security Layer (SASL) Service Names
⟨http://www.iana.org/assignments/gssapi-service-names/⟩.
TLS: RFC 2595.