I saw this topic in the archives and was wondering the same thing myself.
If an autoresponder sends messages to the posters, I send a message to the
offending subscriber (cc'd to their postmaster) telling them what is going
on ,that i am deleting them for it, and suggest they contact their mail
admin for assistance in configuring the responder.  If the response is to
me (the owner), I am sometimes more tolerant.

Can a "Precedence: list|bulk|etc." be inserted in the mail headers?  This
should help with newer versions of vacation.  Of course, there is no
telling what some of these folks are using, and adding to the headers
might even cause other problems.
-- Joe Kelley
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