I've got a puzzling qmail situation (at least to me, but I am not a qmail expert, this is a work-related issue that I'm looking at by default...)
There are about a dozen emails sent to a particular address that have been in the qmail queue on our mailserver for 2 days. In the logs I see each delivery attempt ends with
delivery NNNN: deferral: Connected_to_XXX.XXX.X.XX_but_connection_died._Possible_duplicate!_(#4.4.2)/
All this time, literally thousands of other emails to the exact same address are being sent successfully. There's nothing I can see about the dozen failed messages that is different, although that is the only logical explanation I can think of.
The destination host (XXX.XXX.X.XX) is a machine on our own internal network.
Any suggestions on what I could check? Any way to get additional details on what happened to cause 'connection died'? E.g., perhaps the email server at the destination rejected the messages due to some particular content?
Any suggestions will be much appreciated.
it is possible that the mail is looping. If the mail header contains "Delivered To:" line then qmail-local usually gives a deferral.
Also check the destination server for any logs, if multiple copies of same mail are been hit there for any random reasons.