[Mailman-Users] Huge slowdown reflected in smtp logs

[Craig Pettersen]

Hi All,
  A couple of months ago we added a 35,000 member list to our new mailman
installation.   Checking the mailman smtp logs, we were very please with the
performance - the whole list went out in 250 seconds.  Individual messages
were logging in at a fraction of a second.  Mailings to this newsletter list
go out about every 2-3 weeks.  The first three mailings went out just fine -
one in as little as 43 seconds to all 35000 members.  But suddenly the time
shot up to over 4000 seconds on the fourth mailing, and individual messages
are going out at between 3 and 120 seconds.  Subsequent mailings have had
similar numbers and haven't coincided with any particularly busy times for
the server, nor has any configuration of the server been changed.  We use
qmail, by the way.
   I'm not sure how to account for this huge slowdown.  I suspect it may
have something to do with the bounce system, because it was the fourth
mailing that we first saw a reduction (about 500) in the mailing due to
bounce-disabled subscribers.  Currently there are about 11000
bounce-disabled subscribers which is not particularly a concern since the
list had never been purged before.  I would just like to know if anyone out
there might have a clue as to the cause of the slowdown and if there might
be anything we can do to speed things up.
  Regards,
  Craig