Title: How can I avoid spam on my Mailman list?

Question: I am the owner of a Mailman list and I have noticed an increased
amount of spam that is sent to the list.  Is there anything I can do to
keep the spam from reaching my list members or from having to discard it
myself when it is held for approval?

Answer:

Depending on how your list is used, you have several options for avoiding
spam. The first option is to have Mailman automatically discard all
messages from non-members. To do this, go to the admin pages for the list
at

        http://lists.nmsu.edu/mailman/admin/listname

where "listname" is replaced with the name of your list. Login with your 
list owner password, and follow the Configuration Categories links to 
Privacy Options -> Sender filters. Set the "generic nonmember action" setting 
to Discard and submit your changes.

Note that you can fine-tune your list to allow some specific domains to
post to your list while discarding all other messages. (These domains are
based on the From address of the incoming message and you should be aware
that this address is often forged by spammers.) For example, if you would
like addresses ending in nmsu.edu to be able to post to your list
regardless of whether or not they are members, while still discarding all
other messages from non-members, add the following entry to the "accept
these non-members" setting on the Privacy Options -> Sender filters page
and then submit your changes:

        ^.*nmsu.edu

Similarly, your list can be configured to only allow members to post
without moderation, messages from non-members can be discarded
automatically, and messages from non-member nmsu.edu addresses can
be held for your approval. To do this, put the above entry in the "hold
these nonmembers" setting rather than the "accept these nonmembers"
setting.

Another option is to discard messages from specific domains. Mailman uses
the From address from incoming messages when determining which domain it
is from. Please be aware that the From address is often forged. To enter
domains in the "discard these nonmembers" setting (in Privacy Options ->
Sender filters), put them in the following format:

	^.*domain

e.g.  	^.*msn.com