[Mailman-Users] Slow DNS causes backup in qfiles/ dir

[Phil Suh]

Hello,

I'm new to this list, a longtime mailman user, and now breaking myself in 
as a Mailman administrator.

I run a list with about 2200 members[1], it runs on a FreeBSD box, with 
Postfix 1.1.2 and Mailman 2.0.10.

The problem: on occasion Mailman stops sending mail, and files back up in
the qfiles/ dir. In this case it was not, as suggested elsewhere[2], a
cron problem.

After taking a long look at smtp-failure, it seems that when a email's 
hostname can't be resolved, it results in a long delay in processing a 
message (3 minutes or more). With a 4 or 5 of these messages in the 
qfiles/ dir, the qrunner process get stuck behind these non-resolving 
messages, and never gets around to processing the other messages in the 
queue before it times out.

I believe I've diagnosed the problem correctly. But I'm unsure of how to 
resolve it. Currently, I check on the list on occasion, and when I see 
that smtp-failure is logging bad email addresses, I turn off mail delivery 
for that address, clear the problem files from qfiles/. [I tried 
unsubscribing bad addresses, but that generated a unsubscribe notice, 
which would go into the queue, and cause more problems...] Then the queue 
unclogs. I generally have to discard the problem messages because if I put 
them back in. they just clog the qfiles/ directory again.

Taking a closer look at the the email addresses that failed, if I do a 

  $host baddomain.com

it takes more than a minute before it comes back with 

  'Host not found, try again.'

So my questions are:

1. Have other people experienced this, and what did you do?
2. If I'm not alone in this problem, is there some way of solving this via 
Mailman or my system? It seems wrong to have to go in by hand every 4-5 
days to clear out bad files.  DNS seems to be spotty these days, and it's 
not just the little guys. mx2.eudoramail.com went down last week, which 
caused another clog-up.

Any advice is appreciated. 

Cheers,

Phil Suh

[1] http://cms-list.org/
[2] http://mail.python.org/pipermail/mailman-users/2002-April/018982.html


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