Lately I've been dealing with strange mail loop issues with Courier. Users configure mail forwards using .mailfilter's like:

cc "!pers...@aol.com"

Should Courier fail to deliver the message to the user's external account due to another MTA's aggressive spam filter, overquota account or whatever reason, a delivery failure is sent to the user's local account. In delivering the failure notice, maildrop CCs again the external address, creating an endless loop of delivery failures. This goes until I notice it and I end up with 25,000+ messages in the queue. Courier continues to work fine though, even with a very full queue other deliveries remain speedy. But how can I prevent these loops? Should Courier be detecting a loop and what did I break to keep it from detecting the loop? In a previous thread (see http://sourceforge.net/mailarchive/message.php?msg_id=9664407) I had mentioned that when maildrop sends CCs a Return-Path: header was adding using the real unix user address instead of the virtual LDAP user. At the time, that was undesirable but I believe it prevented these loops, the Return-Path no longer gets added, has the code changed? I've tried turning backscatter on but that doesn't seem to suppress these messages (possibly because they are local until maildrop CCs them?). What should be happening here? Thanks for any clues,

Jay

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