[Mailman-Users] Analysis of reasons for bounce responses

[Richard Barrett]

This is not my problem but one soemone approached me about off list.  
I'll summarise their situation and I would appreciate any thoughts,  
comments, sanity checking on my analysis.

Situation:

1. List admin's domain is hosted by a server run by a hosting company.

2. The server is (probably) running Linux

3. Mailman 2.1.2 is provided on the server with, I believe, CPanel

4. The server's MTA appears to be Exim 4.20 handling both incoming and  
outgoing messages to/from Mailman

5. Mailman list's basically work OK much of the time

6. Periodically messages out from Mailman are being bounced en masse  
leading to the subscriber accounts being disabled

7. The bounce response attached to the bounce action notice produced by  
Mailman when subscribers are disabled in these circumstances is from  
the server local MTA. The MTA lists what appears to be all the  
addresses to which the outgoing message was sent with a note against  
each saying "unrouteable mail domain maildomain.tld". The bounce  
response asserts that this is a permanent failure. The messages are  
each being sent to a number of different mail domains not just a single  
one

8. The list admin with the problem has no access to either the Mailman  
or MTA logs

9. The server administrator is supposedly claiming that these bounces  
are a result of "a bug in Mailman for which no patch is available"

My analysis is:

1. The problem is not obviously due to any bug in Mailman

2. The problem is more likely due to an IP routing problem which  
periodically afflicts the server and its ability to reach the MTAs for  
the mail domains addressed by the outgoing messages

3. The MTA is accepting the outgoing messages from Mailman and then  
finding it has problems of its own in delivering mail which are  
unrelated to Mailman as the origin of the messages

But I have to concede I know nothing about Exim 4.20. I know even less  
about CPanel.

Any thoughts or anatomically feasible suggestions welcome.

------------------------------------------------------------------------ 
-----
Richard Barrett                                      
http://www.openinfo.co.uk