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A number of users on a list had an issue with mail; Mailman messages were being rejected with a 550 error due to a problem with their server.

For some reason, these bounce messages were then appearing on the list. They were then sent out again, going out to the faulty address, and bouncing again, which returned to the list, and so on.

What setting could cause this? I haven't encountered a situation where bounces ended up being resent to the list, instead of going to the list owner. The bounce settings for this list are below:

bounce_processing = 1
bounce_score_threshold = 3.0
bounce_info_stale_after = 7
bounce_you_are_disabled_warnings = 3
bounce_you_are_disabled_warnings_interval = 7
bounce_unrecognized_goes_to_list_owner = True
bounce_notify_owner_on_disable = True
bounce_notify_owner_on_removal = True
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up vote 1 down vote accepted

Sounds like Mailman simply didn't recognize that it was a bounce. There are so many conditions to test for, and so many mailservers, spam filters and non-standard bounce formats. Once in a while one edge case slips through. The Mailman code needs to be modified to identify this new bounce pattern. This used to be fairly common with "Out of office" auto-replies as well.

This is an old post, but it shows you the kinds of things the developers have to go through to keep up with non-compliant hosts.

share|improve this answer
That seems to be the case - the remote server is sending bounces back to the list, and Mailman thinks these are posts. The affected list was allowing non-member posts; I've stopped that, and added mailer-daemon on the remote server to the Hold list. Thanks for the answer! – Austin Nov 16 '12 at 10:18

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