Luis Croker a écrit :
>
> Hi...
>
> I have a mail server with FreeBSD 7.0,
> postfix+amavis-new+spamassassin. We are an ISP and I need to filter the
> spam that our susbribers are sending to internet, the PCs have some
> malware or are botnets. These PCs generates a lot of spam each day.
>
> The server filters a los of Spam but some times the queue is so
> crowded. I have to questions...
> Do you have any recomendation to improve the performance on the server ??
>
> How can I catch more spam than the seerver is filtering ? The server
> blocks many messages but another spam messages goes to internet cause
> the score does not reach the parameters to be blocked.
>


by default, amavisd-new won't add SA headers if the mail is not destined
to a "local" domain. you may need to tweak this.

filtering outbound mail is a bit harder (exceptionally at an ISP). note
that you should not use the PBL (or any "dul" like DNSBL).

consider using policyd (www.policyd.org), it has a rate limiting
functionality. use Version 1 which has been used in ISP environment
(single threaded C daemon). (of course, don't use greylisting.
greylisting is for MTAs, not for MUAs). For questions about this, use
the postfix users list.

Also, as others said, start migrating to submission: port 587 with SASL
authentication. Even if this won't block "motivated" malware authors, it
adds a barrier and is currently the recommended approach. and while you
are in, see if you can also move to TLS (STARTTLS on 587 for standard
compliant MUAs, and the old 465 for others).