[Mailman-Users] Mailman post log failures

Jonathan Dill jonathan at nerds.net
Fri Apr 18 19:27:17 CEST 2008

On Apr 18, 2008, at 1:01 PM, Charles Marcus wrote:

> On 4/18/2008, Jonathan Dill (jonathan at nerds.net) wrote:
>> If you are using a separate e-mail relay, could also be firewall
>> issue,
> Is there by any chance a CISCO router in the mix anywhere?

Yes exactly, I have seen the same type of thing with SonicWALL as  
well--the firewall sends back an RST to kill the connection, and the  
server thinks that the other end dropped the connection and you get  
"Connection unexpectedly closed".  If you have IPS and "deep packet  
inspection" there are even more reasons the firewall could decide to  
kill the connection, even if the allow / accept rules all look  
correct, hopefully there is some sign in the firewall logs if that is  
the case.

Even if there is not a firewall or router and something completely  
different is going on, you can learn a lot by picking apart a packet  
trace off the server or especially the firewall, the "follow tcp  
stream" option in wireshark or ethereal is priceless, then you can  
follow the conversation.  Even if everything is happening in loopback  
(as it should be if it is all supposed to be contained on one server)  
you can still sniff on the loopback connection.  Or you may discover  
that some of the traffic is getting sent out on the wire that is  
supposed to stay on the same box e.g. if DNS or /etc/hosts is not up  
to date.


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