Why is some email from AOL automatically being treated as Spam by MDaemon?

If some email from AOL users is automatically being flagged as spam and routed according to your settings at Security -> Spam Filter then it’s likely that the email already contains a X-Spam-Flag: Yes header before it reaches MDaemon.

This header is being added by AOL when the email looks to be spam as they spam filter all email sent from their customers in order to reduce some of the problems they have had historically with their mail servers being added to DNS blacklists.

Unfortunately, the “X-Spam-Flag: Yes” header is the same header any mailserver using SpamAssassin adds when a message is scored as spam. As some of MDaemon’s spam filtering is based on SpamAssassin then as this message arrives in MDaemon’s local queue, it treats it as spam.

To prevent this, you need to tell MDaemon to strip this header out of the email as it accepts it, so it is then routed through MDaemon normally.

To do so tick X-Spam-Flag in Setup -> Preferences -> Headers: