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Spam on Mailman Lists

To reduce or eliminate spam on mailing lists when using Mailman

The following steps will do two things in mailman:
  1. Discard any message from an email name that does not end in "". (The admin of the list can optionally get a notice of all discarded messages.
  2. Hold all other messages for the administrator to approve. The burden on the administrator is that s/he must approve all messages posted to the list, including those from members. But this will keep all spam (including the ones with spoofed email IDs) from going out to all members of your list. (This solution might be good for low-traffic lists where letting any spam through causes problems, perhaps by annoying a lot of people or some important people.)
What to do in the mailman admin interface:
  1. Under "Privacy options..." choose "Sender Filters".
  2. The first item (for the value default_member_moderation) should be set to "yes".
  3. On the same page, find the item: List of non-member addresses whose postings will be immediately held for moderation. In the box, enter this regular expression: ^.*virginia\.edu$
  4. On the same page, for the next to the last item (generic_nonmember_action), set this to "Discard".
  5. On the same page, for the last item, set this to "yes" if the admin wants to get emails with each message from those that are automatically discarded because they are not from a "" address. (Might be a reasonable thing to do if there is a chance that a legitimate message from outside will come to the list.)
  6. Click "Submit your Changes".
  7. At the top of the page, choose "Membership Management".
  8. At the bottom of the page, for the option "Set everyone's moderation bit, including those members not currently visible", click "yes" and then hit the "Set" button.