Tom,
My environment is postfix, procmail, bogofilter, and Sylpheed-Claws and I had something like that on Sunday.
While reading mail, I noticed a "no subject" message, which often means spam. However this was in a user folder, not the spam folder. When I looked at the file (in its MH directory), it appeared to be truncated at the end of the Received: header line. It's not at all clear what happened. My procmailrc does the following (roughly):
save a copy of every incoming message (before any filtering) in mail.backup.mbx. That copy was fine.
bogofilter then runs and adds its X-Bogosity line.
if spam, copy the message to spam.bogofilter.mbx and deliver it to the admin account, and stop
if unsure, copy the message to unsure.bogofilter.mbx
deliver the message to the recipients mbox
Sylpheed-Claws then retrieves messages for (several) users.
_All_ copies of the message on the server were fine. The only bad copy was on my workstation. Didn't see any abnormal occurrences in the logs.
In any case, I've got my eyes peeled for another occurrence.
Regards,
David