Hi Ernie,
> We are running into an issue where we are seeing a small amount of emails
> sent out with truncated text, lost attachments, etc. This just started
> Monday, and after a few hours seemed to have just "fixed" itself while we
> were still investigating what was happening. After looking on the Internet,
> and seeing a lot of issues with MailScanner and Postfix (I know, we are
> using Sendmail not Postfix on BQ), we can't help but wonder if there is
> something similar happening here. Has anyone else had users report that
> email was missing parts?
MailScanner is - and always has been - just a dirty hack. It sure has
developed over the years and great efforts are still put into it. So it is
constantly maturing and improving. However, it's still a dirty hack.
All the MailScanner scripts that wrap around Sendmail have a tendency of being
a bit spooky and can indeed loose mails, attachments or other bits and
pieces. Espececially under high load it can be that processes related to
MailScanner run out of memory and/or crash. What then happens with the email
being processed depends on what stage of delivery MailScanner currently was.
At best the mail is still in the queue, being processed again sometime down
the road. At the worst? The mail gets lost, garbled or truncated.
So under high load MailScanner may go awry on you. On the other hand:
MailScanner is so ineffective, that it'll drive the load right through the
roof even under moderate email traffic.
I just had the pleasure of looking at a server that was using MailScanner and
which processes roughly 100.000-150.000 emails a day. It was constantly
hovering around 6.80 and 8.50 server load - even with Syslogd shut down to
save CPU cycles during the cron.daily cron runs.
The same server is now running something different which provides equal (or
better) protection, uses Sendmail Milter to tie the virus and spam checking
into the MTA and the box processes the same amount of emails as before. The
load? It's down to a 15 minute load average of 0.18. With logging turned back
on.
My suggestion therefore: Get rid of MailScanner. I don't have half as much
experience with Postfix in regards to customizations as with Sendmail, but
newer versions of Postfix also support Sendmail style Milters as it appears:
http://wiki.linuxquestions.org/wiki/Postfix_with_clamav-milter
So you can install Clam AV Milter and possibly also SpamAssassin Milter (there
are a few Milters for SpamAssassin available).
Of course there is also the somewhat more traditional approach of integrating
Clam AV and SpamAssassin into Postfix - without Milters:
http://www.tedesca.net/bez/homeoff/antispam.html
Any of the above approaches is certainly better than using MailScanner. Just
my $0.02.
--
With best regards,
Michael Stauber
http://www.solarspeed.net