non-existent msgids & duplicate delivery suppression

[Stephen Grier]

Hi,

We are currently running cyrus-imapd-2.1.11 with duplicate delivery
suppression enabled.

One of our users complained that they were not receiving their mail.
Having looked at the logs I noticed a string of entries like the
following:

Jun 25 13:11:43 machine lmtpd[18521]:
duplicate_check:                                         
user.XXXXX          1056537904
Jun 25 13:11:43 machine lmtpd[18521]: dupelim: eliminated duplicate
message to user.XXXXX id

Notice that the message-id is missing. The entries correspond to mail
sent by the same sender which do not contain a message-id header. It
appears that lmtpd has been suppressing mail from this sender, because
it assumes that all mail with a zero length message-id is a duplicate of
the last.

I have noticed that this has been happening on other occasions, where
lmtpd does a duplicate_check and then a duplicate_mark on zero length
message-ids. This raises the possibility that the server is suppressing
messages that are not duplicates, but merely have no message-id header.

Has anyone else seen this happening?. If this continues to happen we may
have to disable duplicate delivery suppression.

Thanks

-- 

Stephen Grier
Systems Developer
Computing Services
Queen Mary, University of London