[Mimedefang] accept, then scan?

[Kimmo Jaskari]

On Thu, 2007-09-20 at 22:20 -0700, Andy Lyttle wrote:
> with SpamAssassin.  Is that possible?  The reason is, on old slow  
> hardware, certain large messages are taking too long to scan (two  
> minutes or more), and in some cases I'm accepting the message but the  
> sending MTA timed out, so I wind up receiving duplicate messages.  In  
> other cases, Sendmail just times out because mimedefang took too long  
> to respond, so Sendmail returning a tempfail.

I had this issue as well, but it wasn't SA that was the culprit, it was
ClamAV. 

I rebuilt my filtering servers from the ground up on a newer OS version
and switched from a command-line Uvscan to Clam, and was getting mail
dupes in droves because it took Clam too long to chew through the mail.

I solved it in three ways - first, made sure my access file in Sendmail
explicitly contained the mail addresses we accept mail for by using a
Perl script to fetch the mail addresses from Exchange (previously,
everything was scanned and sent to Exchange to be refused there, which
obviously was bad). 

Second, I added a Spamhaus ZEN DNSBL check on the Sendmail level
directly, which started rejecting thousands upon thousands of spam on
initial connect; false positives seem to pretty much not happen, no
complaints at all. 

Third - I went back to Uvscan until my two new mailservers (which have
very beefy CPU's) can be taken into use...

/Kimmo