mailq builds up when load average is high

[Shaamil]

Hi All
Could anyone out there please tell me why the mailq builds up when the load average is high.
I have a K370 running 10.20 with + - 1000 users on the system.

[Stefan Farrelly]

The mailq builds up becuase your load average is high because the server is obviously working very very hard and the mailq program isnt a very high priority one. Its simply not enough resources available. Its not really possible to make the mailq (sendmail) daemon work any faster - if your server gets really busy the mail queue is going to go up. Try to reduce the load on your server.

[Ian Box]

As Stefan says, your system is probably overloaded, but there are some tuning praramters in /etc/mail/sendmail.cf, including one 'O QueueLA', Which defines the load average at which sendmail will stop trying to send messages, and will just queue them. You could try defining that value to see if it helps.

[Jeff Schussele · Accepted solution]

Hi Shaamil,

As Ian stated there are 2 load related values in sendmail.cf
They are QueueLA..QueueLoadAverage..defaults to a load avg of 8. System will quit processing the mail queue when that value is reached or exceeded.
The other is RefuseLA..RefuseLoadAverage...defaults to 12. System will refuse any new connections at this value or above.
You could probably increase the QueueLA value a little...possibly to 10-12.
Then remember to
/sbin/init./sendmail stop
/sbin/init./sendmail start
which will restart sendmail with the new parameters.
And causes for the high load values should also be investigated. You may be able to reduce load on the system with careful tuning.

HTH,
Jeff