[Mailman-Users] Strange bounce messages - why is it allowed throughand how do I find out?

[Mark Sapiro]

Lars Bungum wrote:

>I'm running a list of about 500 people, and have encountered a strange
>problem lately, namely that bounce messages from an address
>
>"dummy at not.exist" are being sent to the list.  The subject is like this:
>
>Autoreply: {digest-subject}
>
>and body like this:
>"This email adress do not exist"
>
>so it appears to be bouncing the digest.  The address does not exist,
>and obviously is not a subscribed to the list.  And the posting policy
>is subscribers only.  A lot of messages are being held for moderation
>because the posters are not members (spam).  Still this one comes
>through. 
>
>In the mailman/logs/post log file it just says that dummy at not.exist
>posted to the list at this or that time.
>
>I'm both bewildered and estranged - what is this?  And how do I find out
>why it is allowed to post to the list?

Here's a possible scenario:

A digest is sent to a subscribed address that is no longer valid.

The receiving MTA is broken and sends a "bounce" message to the
Reply-To: address of the digest (instead of the envelope sender,
Sender: or Errors-To: address) which is the list.

Either the envelope sender or some header you use in validating the
poster contains the address the digest was sent to, so the post is
allowed.

--
Mark Sapiro <msapiro at value.net>       The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan