I recently switched from my old gentoo server to a new FC5 server. I opted to go with a qmail-toaster setup because, while I’m perfectly capable of manually making my desired qmail+vpopmail setup, I just didn’t want to spend the personal time doing it. So I figured I would give the toaster project a try. And I have to say that I’m fairly impressed.

A lot of the core technological things that it did were done in basically the same way that I would have done them manually (which is bidirectionally gratifying for me) and there are some bells and whistles that are *nice* but I wouldn’t have bothered setting them up on my own (e.g. qmailmrtg graphical log analysis.)

I did (hopefully did and not still do) have one oddball problem with it. After switching over there were certain servers from which I would continuously get the same message over and over from. Everything in my logs showed a successful delivery, and its not as though the messages were stuck in my queue either, the remote servers would actually reconnect and deliver the message again.

Well for a while I had better things to do with my scant time than deal with this one inconvenient (but not critical) issue. Well today I finally cracked. Its probably because I’ve now gotten one particular message something on the order of 30 times now. Thinking about the problem, and examining my logs it seemed that the only time this happened was when a message was processed by simscan for viruses (clamd) and spam (spamd) at the SMTP transmission level. But that was not the complete story because other messages from other servers did not have this problem even though they went through simscan as well.

On a hunch I figured that the sending mail server was probably only designed to wait X number of seconds (or microseconds) after the finished transmission before expecting to get a status code back from my SMTP daemon. If it takes too long then the remote sending server might just assume the connection was lost and re-queue the message for redelivery. So I disabled spam and virus scanning in simscan

#echo ":clam=no,spam=no,spam_hits=12,attach=.mp3:.src:.bat:.pif" \
  > /var/qmail/control/simcontrol
# /var/qmail/bin/simscanmk
# /var/qmail/bin/simscanmk -g
# qmailctl restart

And the problem *seems* to have gone away. I’m not worried about viruses at this point because I’m running OSX as my desktop, and Thunderbird is usually pretty good about spam… so… no loss for me there.

I’m mainly writing this down here so that if someone were to have this problem, and floundering while searching for an answer, they might have a better chance of finding a helpful hint. Searching for things like redelivery and mail loops on google will yield nothing of any value at present.

Cheers
DK