MailScanner on High Volume Servers

James Ratliff jratliff at
Fri Feb 15 15:51:27 GMT 2002

We've been using MailScanner on a couple of our mail servers for the
past week or so with Sophos and Spamassassin. I thought I would share
some of our experiences and see if it fell in line with what the rest of
you are seeing.
Our main mail server is a dual 1.4 Ghz with 4GB of ram running Redhat
7.2 with Sendmail on the 2.4.17 kernel. It sends and receives roughly
250,000 e-mails per day. When we first installed Mailscanner, we had
several problems with mail delay times going upwards of 45 minutes or
so. It actually got so bad at one point we had to manually proccess the to get mail moving again. After looking at the web page and
reading through the mailing list archive, we set Sendmail to -q1m and
changed the  "Delivery Method = queue" and set "Deliver In Background =
yes" in the mailscanner.conf. This helped trememdously, but we were
still seeing high delays when mail volumes got very high. After watching
the queue and reading through the source, we determined that the delays
were being caused mostly by spamassassin. So I started tinkering with
the  "Max SpamAssassin Size =" setting in the mailscanner.conf. This
setting turned out to be the "magic setting" for us. I eventually had to
move it down to 20000, but mail delay times rarely exceed 8 or 9 minutes
which is acceptable (even if it does let a very few number of spams slip
One thing I have noticed is that even when the mail volumes get very
high, the box load average still never goes above 3 or 4. This leads me
to believe after looking through the code, that an increase in the
number of possible child processes would be very helpful in our
situation. We noticed that this code had been started but commented out.
We were wondering what sorts of problems you were seeing when you tried
running multiple threads. Thanks.

James G. Ratliff
Systems Engineer/Security Analyst
Mikrotec Internet Services
Network Operations Center
1001 Winchester Rd.
Lexington, KY 40505
859-231-1231 Ext. 13

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