* Ansgar Wiechers <li...@planetcobalt.net>:
> On 2015-09-10 Robert Chalmers wrote:
> > I’m currently running postscreen, and am wondering how I would add
> > spamassassin to the main.cf configuration, or are they mutually
> > exclusive?
>
> I'm not sure if they technically can't be used together, but they
> shouldn't be. Spamassassin is rather heavyweight whereas Postscreen was
> designed to be a lightweight zombie deflection tool. You'd lose that
> low resource impact advantage by mixing the two.
They can't *and* it doesn't make sense. See this graph. It shows the various
filter groups in Postfix and the sequence in which they take place. This is
how a message runs through the Postfix filters when a client tries to deliver
a message to Postfix:
connection filter -> session filter -> content filter
Postscreen is a connection filter. It "sees" client IP addresses and it
implements a fake SMTP server. The fake SMTP server does lightweight tests
only. Postscreens job is to keep Postfix' service available. It decides within
very short time if a connection request should be passed on to the Postfix
smtpd SMTP server component. The focus here is on lightweight and maximum
speed.
Spamassassin is a content filter. It "sees" IP addresses, session data and
content. It examines the content for signs indicating a message might contain
spam or ham. It runds hundreds of tests to find out if a message contains
spam or not. It is heavyweight and it takes (very) long to determine a
result.
So technically the two programs take place at different stages during the
delivery process and it is not possible to run a content filter during
the connection stage in a useful way. All the content filter would "see" are
IP addresses - no content.
It wouldn't make sense to expand postscreens' capabilities either to feed a
content filter, because that would sacrifice the use is has been build for.
If you want/need to increase the systems filter effectiveness tell us about
the current problems you face and we can start sharing ideas and concepts.
p@rick
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