[Mailman-Users] duplicate mails on my list

[Nigel Metheringham]

bwarsaw at cnri.reston.va.us said:
> I have recently received a few complaints about duplicates to the
> python-list, so it looks like I will have to spend some time figuring
> this out.  Stay tuned. 

Barry,

I get the feeling there are 2 problems causing this since a few people 
are convinced that some duplications are happening at the MTA stage, 
however all the detailed logging I have seen have been due to MM 
submitting the message to the MTA twice.

This latest variant where a hung MTA and restart causes MM to redeliver 
complete messages may be another form entirely.

The problem I saw and worked round was where the MTA was doing 
recipient address verification during the SMTP transaction - ie each
	RCPT TO ....
was causing a routing/verification operation
On our box, which is relatively low power, at times of stress (ie a few 
10s of incoming list messages within a few minutes), the parallel MTAs 
(in our case exim) and MMs running caused the whole machine to grind 
horribly.  Then it appeared that MM decided that the child doing the 
delivery had taken too long and reran it, thus causing duplication [to 
a segment of the list membership for that message - it was typically 
the last batch of members in the list who got duplicates].

I modified the MTA configs to handle loading better and to *not* do 
SMTP recipient verification for messages injected via the loopback 
interface.  Thats fixed the problem for us.

	Nigel.
-- 
[ Nigel Metheringham                  Nigel.Metheringham at VData.co.uk ]
[ Phone: +44 1423 850000                         Fax +44 1423 858866 ]