[Mailman-Users] Preventing Cross Posting

Mark Sapiro msapiro at value.net
Mon Jul 23 23:57:36 CEST 2007

Bryan Carbonnell wrote:

>Is there anyway to prevent posts from being cross posted across
>several lists on the same Mailman installation?
>I'm running into 2 situations that i'd like to prevent
>1) Cross-posting with several list names in the to or cc headers
>2) Individual identical messages sent separately to different lists
>Is this possible without resorting to a clue-by-four for the offending users?

There's no configuration setting to accomplish this. You could possibly
accomplish 1) by putting some regexp(s) in header_filter_rules for To:
and Cc: headers to recognize 'foreign' list names, but this would be a
maintenance headache unless list names were very stable.

I think 1) might best be accomplished by creating a custom handler (see
to collect all the addresses from To: and Cc: in the local domain and
see if more than one local part matches a list name.

2) is much more difficult as the first message would probably always be
accepted. Also, the Message-ID: might be different across the messages
making that not a reliable indication of a duplicate. You might make
your custom handler create a hash of the message body and save recent
ones in some kind of data store along with info about the list,
sender, etc. and then check each new post to see if it matches one
already accepted.

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

More information about the Mailman-Users mailing list