Introduction

This article is intended to provide information on how to reduce the volume of spam emails and spam subscriptions submitted to a Mailman list. 

---

Applicability

This article is intended for Mailman list owners/administrators

---

Procedure

The following settings will aid in reducing the volume of spam emails and spam subscription requests for a Mailman list.

For spam email submissions:

Specify domains that are not allowed to post

• To ban an entire domain from being able to post to your list and have Mailman automatically discard all messages from that domain, enter the following regular expression in the discard_these_nonmembers setting on the Privacy Options category → Sender filters subsection of the admin pages:

^.*domain$

For spam subscription requests:

1. Navigate to Privacy Options > Subscription Rules
   
   1. Set Advertise this list when people ask what lists are on this machine? to No
   2. Set What steps are required for subscription? to Confirm and approve. (If set, when someone requests a subscription, Mailman sends them a notice with a unique subscription request number that they must reply to in order to subscribe.
      
      

OPTIONAL Use regular expressions in the ban list and 

The List of addresses which are banned from membership in this mailing list. field accepts regular expressions. You can read more about regular expressions in Mailman here. 
NOTE: regex should only be used in Mailman lists if you are familiar with it. REGEXT in Mailman is NOT supported by IST. 
Common regular expressions include:
^(?!.*ualberta\.ca$) will ban all NON ualberta.ca email addresses.

Keywords: mailman, spam, subscription rules, mailing list serve, listserve, blocked domain, banned domain, block domain