REJECT with Before-Queue Content Filter?

[Juerg Reimann]

Hello everybody,

Please excuse my probably rather novice question but I couldn't find any hint on this. The document at http://www.postfix.org/SMTPD_PROXY_README.html says it should be possible to reject an email with a before-queue content filter ... but how would I exactly accomplish this?

What I want to do is reject what spamassassin considers spam (ok, I know the cons, but I really want to do it this way), so what I have in my master.cf is:

smtp inet n - n - - smtpd
-o content_filter=spamfilter:dummy
spamfilter unix - n n - - pipe
flags=Rq user=spamfilter argv=/.../spamfilter -f ${sender} -- ${recipient}

And in spamfilter I have this:

#!/bin/bash
/usr/bin/spamc | /usr/lib/sendmail -i "$@"
exit $?

So how would I have to change my spamfilter in order to have Postfix reject what spamassassin considers spam? A header check on /X-Spam-Level: \*{5,}/ does not work; as in this step Postfix has already accepted the email; it would generate backscatter instead, not what I want...

Thanks a lot for some advice!

[Brian Evans - Postfix List]

On 8/27/2012 3:03 PM, Juerg Reimann wrote:
> Hello everybody,
>
> Please excuse my probably rather novice question but I couldn't find any hint on this. The document at http://www.postfix.org/SMTPD_PROXY_README.html says it should be possible to reject an email with a before-queue content filter ... but how would I exactly accomplish this?
>
> What I want to do is reject what spamassassin considers spam (ok, I know the cons, but I really want to do it this way), so what I have in my master.cf is:

If I were you, I would use spamass-milter or similar because it does
exactly what you describe.
Personally, I use amavisd-milter to do virus scanning as well as spam
checking at the front door.
Just understand that milters are global as per the documentation.

I'm sure there are before-queue filters out there, but you cannot use a
pipe.
You must create/find a front-end that speaks SMTP as noted at the bottom
of the SMTPD_PROXY_README.

Brian

[Noel Jones]

On 8/27/2012 2:03 PM, Juerg Reimann wrote:
> Hello everybody,
>
> Please excuse my probably rather novice question but I couldn't find any hint on this. The document at http://www.postfix.org/SMTPD_PROXY_README.html says it should be possible to reject an email with a before-queue content filter ... but how would I exactly accomplish this?
>
> What I want to do is reject what spamassassin considers spam (ok, I know the cons, but I really want to do it this way), so what I have in my master.cf is:
>

> smtp inet n - n - - smtpd
> -o content_filter=spamfilter:dummy
> spamfilter unix - n n - - pipe
> flags=Rq user=spamfilter argv=/.../spamfilter -f ${sender} -- ${recipient}

This is what postfix refers to as a "simple content filter", and
cannot be used as a before-queue filter.
http://www.postfix.org/FILTER_README.html#simple_filter

To use spamassassin in a before-queue filter, SA will need to be
called either from a milter, or from an "advanced content filter"
that speaks SMTP.


amavisd-new is frequently recommended as a reliable and flexible
advanced content filter that is suitable for use as an
smtpd_proxy_filter.

spamass-milter is frequently recommended as a simple milter for
spamassassin integration.

Although the setup and protocol of smtpd_proxy_filter vs. milter is
very different, overall system load/efficiency is largely the same,
making the choice mostly a feature set of a particular product.



-- Noel Jones

[KSB]

On 2012.08.27. 22:15, Brian Evans - Postfix List wrote:
> I'm sure there are before-queue filters out there, but you cannot use a
> pipe.
> You must create/find a front-end that speaks SMTP as noted at the bottom
> of the SMTPD_PROXY_README.
>
> Brian
>

For example spampd.
__
KSB

[Ralf Hildebrandt]

* Juerg Reimann <j...@jworld.ch>:

> Hello everybody,
>
> Please excuse my probably rather novice question but I couldn't find any hint on this. The document at http://www.postfix.org/SMTPD_PROXY_README.html says it should be possible to reject an email with a before-queue content filter ... but how would I exactly accomplish this?
>
> What I want to do is reject what spamassassin considers spam (ok, I know the cons, but I really want to do it this way), so what I have in my master.cf is:
>
> smtp inet n - n - - smtpd
> -o content_filter=spamfilter:dummy
> spamfilter unix - n n - - pipe
> flags=Rq user=spamfilter argv=/.../spamfilter -f ${sender} -- ${recipient}

That's not possible to use in a smtp_proxy_filter setup, since it uses
a "pipe" instead of a filter that speaks SMTP.

Use a milter or amavisd-new (or, for that matter, any filter solution
that speaks SMTP).

--
Ralf Hildebrandt
Geschäftsbereich IT | Abteilung Netzwerk
Charité - Universitätsmedizin Berlin
Campus Benjamin Franklin
Hindenburgdamm 30 | D-12203 Berlin
Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
ralf.hil...@charite.de | http://www.charite.de