Provided by: vrfy_990522-6_amd64
vrfy - Verify electronic mail addresses
vrfy [options] [-v] address [host] vrfy [options] [-v] -f [file] [host] vrfy [options] [-v] -p domain vrfy [options] [-v] -T domain [name]
vrfy is a tool to verify electronic mail addresses. The only required parameter is the address to be verified. The actual verification will be carried out at the remote machine where mail to the given address would normally be delivered. This may be a mail exchange host and not the final destination host. If an explicit host is given as the second argument on the command line, the specified address is verified at that machine. The output of the program shows whether or not the address can be handled at the contacted host. Error messages will be printed if the address is invalid. If the address is recognized, the output shows the remote host's notion of the (possibly translated) address. If it represents a local user at that host, additional information about the user may be displayed. Note that if the address is accepted by the contacted host, but this is not the final destination host, one still cannot be sure that the address represents a valid recipient. It is a handy tool to verify local mail addresses. If you have set up a .forward file, you can verify your own address to check that the forwarding is done properly. If you specify an arbitrary name, you can check whether this resolves to any valid recipients.
SPECIAL OPERATION MODES
Some flags put the program in a special operation mode. FILE MODE If the -f option is specified, the program enters a special file mode. The (optional) parameter is the name of a file containing electronic mail addresses, such as used for mailing lists. Verification of all addresses present in the file is attempted. If no filename is specified, vrfy acts as a filter and the addresses to be verified are read from standard input. PING MODE If the -p option is specified, the program enters a special ping mode. The required parameter is an electronic mail domain for which it will be verified whether the corresponding mail exchangers are currently responding to SMTP requests. ETRN MODE If the -T option is specified, the program enters a special etrn mode. The required parameter is an electronic mail domain. An ESMTP ETRN command will be delivered to its corresponding mail exchangers. An optional name is used as the ETRN parameter. If not specified, the local host name is used instead. ETRN is defined in RFC 1985, and is implemented in sendmail 8.8. RECURSIVE MODE If the -L level option is specified, the received replies to an address verification are recursively verified up to level levels deep. This is handy for checking mailing list expansions, and detecting possible mail forwarding loops. Recursion stops automatically if the reply represents a local recipient address, or in case a forwarding loop is detected. If the received reply is the same (modulo comments) as the address that was asked for, the request is retried at its domain itself, unless this was the machine we just queried, or it is not an internet domain host. The option -R is equivalent to ``-L 17''. This is the maximum hop count normally used during actual mail relaying. This option also implies ``-s''.
-v Sets verbose mode. Prints the action the program is going to take. If specified as -vv, very verbose output is printed. The SMTP transactions with the remote host are shown in detail. If the verbose mode level is set to 3 with -vvv, the actions taken by the remote host are shown, such as alias and forward expansions. This can be quite amusing. The remote host must support the SMTP VERB command for this to work. In ping mode, the verbose mode level 3 will cause an extra SMTP command HELO to be generated. -d Prints debugging output showing the various phases of the SMTP connection with the remote host. This is normally not of any interest. Also prints various messages that are otherwise shown in very verbose mode. If specified as -dd, in addition all nameserver query transactions are shown in detail. A level 3 debug mode -ddd will not make any SMTP connections at all. -a If multiple mail exchange hosts were found, this option will cause the operation to be carried out at each of these hosts. Normally only the primary mail exchanger is contacted. -l Sets local mode for error handling. Address syntax and parsing errors are handled entirely by the program. The default is to pass faulty addresses to the local host to get the official error messages. -s Strips all comments from full address specifications, and presents only the plain address to the remote host to be verified. Some hosts may get confused when a multiple bracketed address is presented. This option is implied when -R is given. -e Uses the EXPN command instead of the VRFY command. Some systems may have different treatment for these commands, so this option may be a possible alternative. By sendmail V5 they are usually treated the same, but not by the sendmail V8 versions. In case treatment is different, the VRFY command will just show whether the presented address is valid or not, but the EXPN command will return alias expansions, if appropriate. Some systems allow VRFY, but disallow EXPN for privacy reasons. -h This option causes an SMTP HELO command to be issued to the contacted server before subsequent commands are attempted. Servers can be configured to refuse commands unless a HELO command is given first. The HELO is not issued by default, since old versions of sendmail refuse SMTP connections originating on the same machine (i.e. if the domain name in the HELO command is its own name). -H Similar to the -h option, but now the ESMTP EHLO command is tried first. If the contacted server does not understand this, the SMTP HELO command is tried next. -n Many non-sendmail hosts do not, or incorrectly or incompletely, implement the VRFY command. Other systems have VRFY or EXPN disabled for privacy reasons. This option uses an alternative protocol suite with the regular HELO, MAIL, RCPT and RSET commands. This gives only a global indication whether the recipient is valid. Recursive mode is not possible, and will be disabled. -S sender Defines an explicit envelope sender address to be used in the MAIL command during the alternative protocol suite, to overrule the default empty sender address ``<>''. This option implies ``-n''. -c secs Sets a connect timeout value to override the default timeout of 6 seconds. This may be necessary if it takes considerable time to connect to the remote host. -t secs Sets a read timeout value to override the default timeout of 60 seconds. This may be necessary if it takes considerable time for the remote host to assemble all addresses in long mailing lists.
Default options and parameters can be preset in an environment variable VRFY_DEFAULTS using the same syntax as on the command line. They will be evaluated before the command line arguments.
vrfy sets up an SMTP connection with the remote host where the verifying is to be carried out. SMTP is the TCP/IP protocol for electronic mail exchange. If the given host does not speak SMTP, the error message "Connection refused" is printed. If the SMTP protocol is blocked, a "Host is unreachable" message is printed. If the remote host doesn't respond in time, you will get a "Connection timed out" message. The remote host must support the SMTP VRFY command for doing the verification. If not, a "Command not implemented" is printed.
The following strategy is used to find the remote host where the verification is to be carried out. a. If an explicit verification host is specified, that host is contacted unconditionally. b. If the address to be verified has no domain part after an '@' sign, it is supposed to be a local recipient and will be verified at the local host. c. If the address contains a domain part after an '@' sign, mail exchange hosts will be fetched for that domain. If no such mail exchangers are found, the domain part is supposed to represent a specific host, and that host itself will be contacted. d. If mail exchangers were found, the verification will be carried out at the primary mail exchange host. e. If the -a option was given, and multiple mail exchangers exist, the verification is also carried out at all other mail exchange hosts. f. For the pseudo domains ".uucp" and ".bitnet" a specific server can be compiled-in. The default is to contact the local host. g. If no mail exchangers were found for an unqualified single hostname, the local host is contacted by default. The actual meaning of such addresses depend on your local strategy.
Environment variables can be used to overrule several compiled-in defaults. VRFY_LOCALHOST This is your nearest host running the sendmail daemon. It is contacted in case local addresses without a domain are given. Also (unless the -l is given) when domain parsing errors were encountered, assuming that this host can give a more appropriate error message. The default value is localhost. VRFY_UUCPRELAY This host is contacted when a .uucp address is specified. You probably won't get much useful information. The default value is localhost. VRFY_BITNETRELAY This host is contacted when a .bitnet or .earn address is specified. You probably won't get much useful information. The default value is localhost. VRFY_SINGLERELAY This host is contacted when a single unqualified host name could not be resolved to a fully qualified MX domain host. It is assumed that single hosts in your own domain can be resolved, i.e. they have an MX record. It depends on your local strategy for unqualified hosts what they mean: a .uucp host, a .bitnet host, or just a local host without MX. The default value is localhost.
Some hosts have a lousy VRFY handling. Sometimes the command is not implemented at all. Other hosts are willing to verify only local recipients. The "-n" option may be necessary. Other servers may refuse the VRFY command for privacy reasons. If the verification is not performed at the final destination host, one cannot be sure that the given address is valid.
Note the following subtle differences if you want to check an existing mailing list list. Suppose that ``list-users'' is the local alias to include the actual file ``/mail/lists/list-users'' with recipients. The command ``vrfy list-users'' will verify the proper expansion of the mailing list at the local host. No remote hosts are contacted to verify addresses. The command ``vrfy -f /mail/lists/list-users'' will verify each individual address at the appropriate remote hosts. The same effect can be reached when you give the command ``vrfy -L 1 list-users''. Use a higher recursion level if you want to see further expansion of the mailing list.
Eric Wassenaar, Nikhef-H, <email@example.com> 971114 vrfy(1)