SpamSieve has been my indispensable second line of defense for many years. My first line has been the spamfilter we use at our company, which was SpamAssassin, but which we recently transitioned to mailroute.net.
I was attempting to use SpamSieve to “teach” mailroute.net about spam that sneaks by it by forwarding the message to their abuse report email. However, I noticed that the SpamSieve mail rule was sending every message.
I then changed the rule so that it simply changed the background of the message to gray. When I applied the rule to my inbox every message had the gray background.
I reinstalled my SpamSieve Apple Mail plug-in and checked the SpamSieve mail rule.
The mail rule is “If any of the following conditions are met: Message Type is Mail, Perform the following actions: Set Color of background Gray”.
I didn’t change anything else. Now all messages are tagged as spam by SpamSieve.