[Mailman-Users] Mail Delay

[S. Backman]

I'm running several lists with a combined membership of about 1,000 users.
About 4 months ago I suddenly started noticing extreme delays in mail
delivery.  Originally, we had a turn around time of about 3-5 minutes.  Now
we are looking at a 45 - 90 minute turn-around on every email.  We are
posting approximately 100 emails per day.  There was no sudden increase in
membership or anything else that we can specifically point to that would
cause this delay in mail delivery.  All mail seems to hit the server within
a few minutes but it's held up at the server for all this time until it is
finally released.  It's either mailman or sendmail - or something else -
that's causing this problem.  We're not sure what.  Anyone seen this issue
before?  Can you help?

Mailman Version: 2.1.3
OS: Redhat Enterprise Linux 3
Dual CPU Xeon processors
1 GB RAM

Thanks

S. Backman