9.3 Using mailfromd with Postfix

To configure postfix to work with your filter, you need to inform it about the socket your filter is listening on. The smtpd_milters (or non_smtpd_milters) statement in /etc/postfix/main.cf serves this purpose. If the filter is to handle mail that arrives via SMTP, use smtpd_milters. If it is to handle mail submitted locally to the queue, use non_smtpd_milters. In both cases, the value is a whitespace-separated list of socket addresses. Note, that Postfix syntax for socket addresses differs from that used by Sendmail and mailfromd. The differences are summarized in the following table:

For example, if your mailfromd listens on ‘inet://127.0.0.1:4111’, add the following to /etc/postfix/main.cf:

smtpd_milters = inet:127.0.0.1:4111

Mailfromd uses Milter protocol version 6. Postfix, starting from version 2.6 uses the same version. Older versions of Postfix use Milter protocol 2 by default. Normally, it should not be a problem, as mailfromd tries to detect what version the server is speaking. If, however, it fails to select the proper version, you will have to instruct Postfix what version to use. To do so, add the following statement to /etc/postfix/main.cf:

milter_protocol = 6

The way Postfix handles macros differs from that of Sendmail. Postfix emulates a limited subset of Sendmail macros, and not all of them are are available when you would expect them to. In particular, the ‘i’ macro is not available before the ‘DATA’ stage, which brings two consequences. First, mailfromd log messages will not include message ID until the ‘DATA’ stage is reached. Secondly, you cannot use ‘i’ in handlers ‘connect’, ‘helo’, ‘envfrom’ and ‘envrcpt’,

If you wish to tailor Postfix defaults to export the actual macros used by your filter, run mailfromd --dump-macros and filter its output through the postfix-macros.sed filter, which is installed to the prefix/share/mailfromd directory, e.g.:

$ mailfromd --dump-macros | \
  sed -f /usr/share/mailfromd/postfix-macros.sed
milter_helo_macros = {s}
milter_mail_macros = {client_addr} {s} {f}
milter_rcpt_macros = {rcpt_addr} {f} {client_addr}
milter_end_of_data_macros = {i}

Cut and paste its output to your /etc/postfix/main.cf.

For more details regarding Postfix interaction with Milter and available Postfix configuration options, see Postfix before-queue Milter support.