Domino Mail rule set to Reject causes mail to be deleted instead.

Problem

A message which should have been rejected back to the sender instead is deleted by the SpamSentinel Router server task and a entry in the Domino log states "SSRouter: Message rejected by mail rule.  Deleting message."

Example rule:

When SpamSentinel is in place, the sending server never knows what happened to the message because it just disappears.

Background Information

This can only happen when SpamSentinel is running in a Standard configuration since that is the only installation type which uses a SpamSentinel Router server task.

Solution

When a Domino server Mail Rule calls for a message to be rejected and SpamSentinel Router attempts to write a message matching that rule into the server mail.box, the message will always be deleted.  This behavior is by design.

The best solution is to see if the mail rule can be deprecated in favor of finding a way within SpamSentinel to force matching messages to be classified as Spam.