Carnegie Mellon University School of Computer Science

Mailman Administration: Five Important Settings

All of these settings can be found within the Mailman Administrative Web Interface.

Identifying List Administrators

On the "General Options" page for your list, specify the Administrator(s) by SCS Kerberos principal ID(s). For example:


If you often use WebISO to access campus services with your Andrew Kerberos ID, adding that ID to the Administrators group will allow managing your mailing list under either identity. For example:


Administrator Email Addresses

This field must contain one or more valid email address, none of which need be the same as the Administrator's Kerberos ID(s). Mailman will send administrative notices to this address(es).

Limiting Message Size

It is good practice to limit the size of messages distributed through a mailing list. Sending multiple copies of a large message eats up network bandwidth and storage space and may cause other failures, as well. On the "General Options" page, Mailman offers the ability to set a message-size ceiling, which the Administrator can later adjust as needed. The current default limit is 40,000 characters, which value will stop most messages having attachments.

Banning Specific Addresses

On the "Privacy" options page, Mailman offers the ability to ban specific addresses from posting to the mailing list. This option is useful if you wish to block only a few addresses. Enter prohibited email addresses, one per line, in standard format. For example, if you add the entry below, this will automatically discard any mail posted from that address.

Allowing Nonmember Posts

Found on the "Sender Filters" page, this option can sometimes lead to confusing behavior. When a message to the list does not appear to come from a list member, one of the following actions will apply:
  • Accept: Distribute the mail as usual
  • Hold: Await Moderator approval
  • Reject: Bounce the message back to the sender
  • Discard: Silently delete the message without sending to the list or notifying the sender
The appropriate configuration here depends on several factors: whether the list is private, the amount of traffic the list receives, and others. In general, in our current spam-laden environment, when a message comes from a nonmember, it should either be held for moderation or discarded. The only exception is a truly open list where people don't care about spam.

Administrators can create special lists for addresses that Mailman should always "Accept," "Hold," "Reject," or "Discard." See about creating a restricted-privilege group.

Due to potential entanglements with spam, we do not recommend the "Reject" action.

If the default action for nonmember posts is "Discard," even valid members will unable to post from nonmember addresses or addresses selected by other nonmember filters.