tuning for high volume (FAQ 11)

[Jeff A. Earickson]

Y'all,

   I put mailscanner into production mode on my mail server today, a
two-cpu D-class HP system.  I had previously tested mailscanner on both
Sun and HP systems (using sophos) and it looked like the ticket for
my virus woes.

   Since the D-class isn't the world's fastest machine for 3000 users,
I spent most of the day staring at my mail queues, backlogs, thruput,
etc.  I tried both the default installation, and the "queue mode"
suggestions of FAQ 11.  I am not totally convinced that background
delivery mode is working correctly, but I'll look at that more tomorrow.

   The I dug out the Bat Book and read more about processing queues.
Here is the scheme I finally came up with for my site, following FAQ 11.

  * Delivery method = queue  (like FAQ 11)
  * Deliver in Background = yes (like FAQ 11)
  * sendmail -bd -ODeliveryMode=queueonly -OQueueDirectory=/var/spool/mqueue.in
    (launched via sendmail boottime start script)
  * sendmail -q15m, also launched via boottime start script
  * crontab job for local recipients only every minute  (my wrinkle)

The crontab entry looks like:

0-59 * * * * /usr/sbin/sendmail -qR at colby.edu
                                    ^^^^^^^^^
                                    your domain here

The idea here is to get email bound for local recipients in my domain
("colby.edu") delivered fast by processing *only* the local recipient
stuff once a minute.  Anything outbound to a remote site can wait for
the 15 minute queue started with the boot script.

   The "sendmail -q1m" suggestion of FAQ 11 does not work, because email
bound for local recipients is mixed in with remote sites that may not
DNS resolve.  So "sendmail -q1m" does not distinguish between messages
that can be resolved quickly (ie, domains you have DNS control over)
and those that can't.  One bad remote DNS resolve hoses up the whole queue.
My crontab keeps the local stuff moving, and leaves the poky remote stuff
for the queue that runs less often.

** Jeff A. Earickson, Ph.D                         PHONE: 207-872-3659
** Senior UNIX Sysadmin, Information Technology    EMAIL: jaearick at colby.edu
** Colby College, 4214 Mayflower Hill,               FAX: 207-872-3076
** Waterville ME, 04901-8842
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