Provided by: mailfilter_0.6.2-1build1_i386
mailfilterex - Mailfilter configuration file examples
For a description of the rcfile format and its keywords see the
mailfilterrc(5) man page or get a basic set of options from either the
INSTALL file or the doc/ directory of the Mailfilter distribution.
This man page contains several configuration examples and real-life use
cases for the Mailfilter program.
If not stated otherwise, the following examples assume you are using
basic Regular Expressions, the default of Mailfilter. General
information on Regular Expressions can be found in the regex(7) man
page or in any good book on Unix/Posix. You could also use slightly
modified examples from procmail(1) if it is available on your system.
To create a very restrictive set of filter rules at least two keywords
should be used: ALLOW and DENY. DENY could match all messages coming
from an annoying public mail service, while ALLOW matches messages from
a good friend who also uses this annoying public mailer.
DENY = ^From:.*public-mail.com
ALLOW = ^From:.*firstname.lastname@example.org
These two lines are enough to block all but your friend’s e-mail from
the public-mail.com domain.
In general case-sensivity is controlled by the REG_CASE keyword. Having
Mailfilter treat expressions case-insensitive is almost always more
REG_CASE = no
DENY = ^Subject:.*win money
In this example Mailfilter would delete all messages with subject lines
like ‘WIN MONEY’, ‘Win Money’ or any other mix of capital and non-
capital characters. REG_CASE makes filters ignore the case.
A more complex set up can be achieved by additionally using the
DENY_CASE = ^Subject:.*BUSINESS
In this example only e-mails that have ‘BUSINESS’ in their subject
match the filter, even though in general Mailfilter ignores the case.
So in this example all messages with ‘business’ or ‘Business’ in their
subjects would not be affected by this filter.
Such an option is very useful if you are not interested in commercial
bulk mail that offers amazing business opportunities, but in all your
business partners who contact you by e-mail.
The keyword ALLOW can be used to override any spam filters. Similar to
the earlier example ALLOW defines a ‘friend’.
ALLOW = ^Subject:.*mailfilter
Adding this rule to the rcfile would mean all messages that contain
anything about Mailfilter in their subject lines can pass the spam
filters. But even friends tend to send large e-mails sometimes to share
their joy about the latest joke that just made the round in their
office. In such cases a limit can be defined that affects particularly
MAXSIZE_ALLOW = 500000
Setting MAXSIZE_ALLOW to 500000 means no message can be larger than 500
kBytes. (Scanned ‘office-jokes’ are usually around that size.)
Negative Message Filters
In order to create a very restrictive spam protection it can be more
useful sometimes to define which e-mails should not be deleted
instantly and consequently get rid of messages that can not be matched
to this criterion - rather than vice versa. This can be achieved by
using negation. The typical use case is looking at the message tags
‘To:’ or ‘Cc:’ of an e-mail.
DENY <> ^(To|Cc):.*my-email@address\.com
Having added such a filter to your personal rule set keeps away a lot
of spam that is not directly addressed to your e-mail account. Since
this is a very aggressive way of filtering, you are well advised to
keep your ‘friends list’ up to date. Also note that the above example
works only with extended Regular Expressions.
Instead of setting up spam filters, it is also possible to define
scores which can be accumulated until a certain threshold is reached.
This is very useful to delete advertisements on mailing lists, for
instance. Highscore marks the threshold:
HIGHSCORE = 100
SCORE +100 = ^Subject:.*viagra
SCORE +100 = ^Content-Type:.*html
SCORE -100 = ^(To|From):.*my_mailing_list
This simple example is useful to delete mails with a score equal to or
greater than 100, i.e. if someone sends an HTML mail to
my_mailing_list, the message will reach score 0. However, should an
HTML mail regarding Viagra reach the list, then the message will
classify as spam, because it reached an overall score of 100.
The MAXSIZE_SCORE keyword can also be used to add to the accumulated
score for an e-mail. The following will cause all emails not directly
addressed to the recipient and greater than 60000 bytes in size to be
deleted (a useful way of rejecting many common MS targeted worms and
trojans which can clog up your inbox).
HIGHSCORE = 100
MAXSIZE_SCORE +50 = 60000
SCORE +50 <> ^(To|Cc):.*email@example.com
This is a less aggressive way of dealing with e-mail sizes than the
using the MAXSIZE_DENY keyword. Note that this example (by using the
expression (To|Cc):.*firstname.lastname@example.org) works only with extended
General Message Size Limits
It is always a good idea to define a very general size limit for e-
mails. Mailfilter uses the keyword MAXSIZE_DENY for that purpose.
MAXSIZE_DENY = 200000
Setting it to 200 kBytes can save you a couple of hours, depending on
how much mail you get everyday. Messages bigger than that get deleted
on the server, unless they match any of the ALLOW rules. To achieve
maximum efficiency it makes sense to use both MAXSIZE_DENY and
MAXSIZE_ALLOW. No one should block up your mail box, no ‘friends’, no
A rule of thumb is to be twice as tolerant towards friends than you are
towards anonymous people.
Note also the use of the MAXSIZE_SCORE keyword mentioned above, as a
less aggressive way of dealing with message sizes.
Dealing with Duplicates
Most people want to download a message only once, even though it might
have been sent to two or three of their accounts at the same time. The
DEL_DUPLICATES = yes
will take care of duplicates and makes sure that only one copy of a
message has to be delivered.
Normalisation of Message Subjects
Every now and then some clever sales person comes up with the brilliant
idea to wrap spam in funny little characters. If you get a message with
a subject line similar to this one ‘,L.E-G,A.L; ,C.A-B‘L‘E, .B-O‘X‘’,
then ordinary filters would fail to detect the junk.
NORMAL = yes
Adding this directive to the rcfile tells Mailfilter to ‘normalise’
subject strings, i.e. leave in only the alpha-numeric characters and
delete the rest. ‘,L.E-G,A.L; ,C.A-B‘L‘E, .B-O‘X‘’ would then become
‘LEGAL CABLE BOX’ which can easily be matched to a spam filter.
Note that Mailfilter first tries to match the original subject string,
before it checks on the normalised one.
Since Mailfilter deletes e-mails remotely, before they have to be
downloaded into the local machine, it is also important to know what is
going on while the program is being executed. The least you should do
is define a proper level of verbosity and a log file.
LOGFILE = /home/username/logs/mailfilter.log
VERBOSE = 3
Level three is the default verbosity level. Using it Mailfilter reports
information on deleted messages, run-time errors and dates to the
screen and the log file.
Extended Regular Expressions
For some applications the basic Regular Expressions are not good
enough. If you know the syntax and use of the extended type, use the
REG_TYPE keyword to switch modes in Mailfilter.
REG_TYPE = extended
Extended expressions are more flexible, but also more sensitive towards
syntax errors and the like. Know what you are doing if you choose to
If you are new to Regular Expressions and new to Mailfilter, you might
want to experiment a bit, before you accidently delete messages for
real. For such cases Mailfilter provides two keywords. TEST can be used
to only simulate the deletion of messages and SHOW_HEADERS displays all
e-mail headers that get scanned by the program.
TEST = yes
SHOW_HEADERS = yes
Use this setup if you are not yet comfortable with the concept of spam
filtering. It may help to understand Regular Expressions better and how
to use them.
mailfilter(1), mailfilterrc(5), procmailrc(5), procmailex(5), regex(7)
Copyright © 2000-2004 Andreas Bauer <email@example.com>
This is free software; see the source for copying conditions. There is
NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR