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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

https://mailman.u.washington.edu/mailman/admin/listname
where "listname" is replaced with the name of your list. Once you have logged on with your UW NetID and password, 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 washington.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:

^.*washington\.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 washington.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
Yet another option is to have Mailman discard messages with high spam scores. This option is under Privacy Options > Spam filters. Enter the following in the "header filter rules" setting:
X-Uwash-Spam: Gauge=XXXXXXXX
The eight Xs represent a spam score of 80%. This will discard all messages with a spam score of 80% or higher. You can adjust the number of Xs that you use for a lower or higher threshold. You are limited, however, to increases or decreases of 10%. After you add the above line to the setting, select "Discard" as your action and submit your changes. (If you want to be notified of deleted messages matching the spam filter, select "Reject" rather than Discard as your action.)

If you want to discard messages with specific words in the subject line, use the "header filter rules" setting with the following entry:

Subject: .*word
where you replace "word" with the word or phrase you want to match. Again, choose "Discard" as your action and submit your changes.

Date: 08/2005 Author: R. Skiver Thompson