9. Filtering Spam

Spam can be very annoying to subscribers, moderators, and owners of maillists. Subscribers stand an increased risk of receive copies of spam even if they have taken good care over the configuration and management of their own email account; Moderators can be swamped with moderation messages relating to spam that has arrived at the list address; Owners may receive spam that has been detected as (un)subscription requests, complaints from list users, and complaints from third parties who have ended up involved.

9.1. Basic List Configuration to Block Spam

Settings configuration panel

In the Settings panel there are two Spam filtering options that control how the Oxmail spam scoring system is used to reduce spam on your maillist: Enable and Level. By default these options ignore spam scoring - all mail goes through. This is to ensure that a newly create list will faithfully transmit all posts.

A moderate setting that will significantly reduce spam is to tick the Enable option, and leave the Level at the default value of 5.

9.2. Other Options for Controlling Spam

Various other list configuration options have the potential to combat spam as well, but generally affect list operation too. Areas to consider include:
  • Subscription policy: if you manually control list membership and do not provide a list archive then turning off Subscription option 1 can reduce spam, and "back-scatter" resulting from spammers sending mail to the (un)subscription / archive addresses leading to an automated maillist response being sent to the (often forged but valid) sender address used by the spammer
  • Posting options: options 1, 2, and 5 can be used to prevent the list from accepting spam sent from any email address except those specified in your list configuration
  • Header-based filters: configuring your list to reject mail with the Precedence: bulk or Precedence: junk may help to block some forms of circular or unsolicited commercial email
With all of these later options however, there is a risk that you will be altering the behaviour of your list in an undesirable way, and also that some user set-ups result in email being generated that is blocked by some of these settings.

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