Validate Subject Lines
You can limit messages to your list, based upon the start of the Subject Line.
If your list needs a bit more structure, consider using
subject tags. Subject tags require the subject line of an incoming
message to meet certain requirements before being sent on to the
Subject tags are one-word categories added to the front of a
subject line, and can be customized to your own list needs.
Any mailing list might use tags such as ADMIN for list
administration emails and MISC for general or off-topic emails. A
mailing list on controlling clutter might use tags such as TIP for
helpful hints, TASK when inviting others to participate in a cleanup
challenge, and SUCCESS for announcing what they've accomplished.
Email not including current subject tags will be sent back to
the sender, with a note that the post didn't go through and a list of
current subject tags, to help the sender figure out what their subject
line should be.
Using these can also prevent spam messages sent by a
subscriber's hijacked machine from reaching your membership.