Rejecting unsolicited mail

Procmail is very powerful, but at the cost of complexity. A minor syntax error can cause all e-mail to be bounced and lost and so unless you are familiar with it you should not use it for SPAM filtering and protection. Using SpamAssassin and filtering in your e-mail client works well, is much less complex, and is not as dangerous with losing e-mails. We provide a link to some good procmail recipes in our documentation. However useful documentation for procmail would not belong in the control panel as a popup, it is a tool that requires time to learn to not be dangerous.

If you want to discard all messages from xx@yyy.zz, the rule (placed in the "manual procmailrc" field for your mailbox in the control panel) would be:

:0:
* ^From:.*\<xx@yyy\.zz\>
/dev/null

This is a variation on our Filtering by Sender example, using ".*\<xx@yyy\.zz\>" as the regular expression (ie, the pattern) to match, and "/dev/null" as the location to which the message should be moved. We have some more examples here: Managing Email Automatically.

Note that if you choose to use manual procmailrc rules on your mailbox, this will override all of the spam-related settings on your mailbox. So, for example, if you have "enable spam protection" checked for your mailbox and are filtering spam to a folder named "Spam", you will need to re-implement that as a procmail rule, like this:

:0:
* ^X-Spam-Level: \*\*\*\*\*
.Spam/

Finally, as John mentioned in his answer, procmail is a powerful tool, and if you're not careful with the syntax, you might end up losing mail or moving it to the wrong location. The examples I've provided should work, but be sure to test them thoroughly.

Hope that helps!