How to configure multiple postfix content filters?

[Patrick Ben Koetter]

* Mike Schleif <mike at mdsresource.net>:
> Centos:  7.2.1511 (Core)
> postfix: 2.10.1
> amavisd-new: 2.10.1
> 
> This postfix server was designed to run as follows, which it has done for
> several months without incident:
> 
> Original filter-only:
> master.cf:
> smtp  inet  n  -  n  -  -  smtpd
>   -o content_filter=filter:dummy
> 
> filter  unix  -  n  n  -  10  pipe
>   flags=Rq user=filter null_sender=
>   argv=/var/spool/filter/bin/filter.sh -f ${sender} -- ${recipient}
> 
> 
> Now, I'm tasked with retrofitting spamassassin on same host, which works
> using
> following configuration:
> 
> Spamassassin-only:
> master.cf:
> smtp  inet  n  -  n  -  -  smtpd
>   -o content_filter=spamassassin
> 
> spamassassin unix -  n  n  -  -  pipe
>   user=spamd argv=/usr/bin/spamc -f -e
>   /usr/sbin/sendmail -oi -f ${sender} ${recipient}
> 
> 
> Our problem is using _both_ spamassassin and filter, preferably in that
> order.

amavis seems a little over if all you need is spamassassin. You might get away
with less, if you hook spamassassin into Postfix via the spamassassin MILTER
program "spamass-milter".

Using spamass-milter you will be able to pre-queue scan messages. Spamassassin
can classify the messages and add a score. Then the message will be accepted,
written to the queue and sent of to your filter.sh script.

In pseudo-code:

smtp  inet  n  -  n  -  -  smtpd
  -o smtpd_milters=inet:127.0.0.1:20025
  -o content_filter=spamassassin

spamassassin unix -  n  n  -  -  pipe
  user=spamd argv=/usr/bin/spamc -f -e
  /usr/sbin/sendmail -oi -f ${sender} ${recipient}


inet:127.0.0.1:20025 would be where the spamass-milter listens for incoming
connections. It would pass on the message via spamc to spamd. The scan result
would be handed back in reverse order.

p at rick

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