I use Kerio Connect as my mail server (essentially a cross platform Exchange clone). Kerio is great for small businesses who want to self-host email, but its built-in anti-spam features are not as powerful as they could be. I am starting to write a how-to for the Kerio forums for using EFA in front of Kerio for more robust spam protection, while also taking advantage of Kerio's built in protection features such as Sophos AV scanning and a Bitdefender-based anti-spam/anti-phising analysis (which is not very accurate at all).
Kerio supports third party front-end and filtering services in two ways:
- (1) it can sort "Junk" mail to a user folder using the headers. For messages that should be moved to the Junk E-Mail folder the message header must be "X-Spam-Flag: YES".
(2) you can configure back-end Kerio Connect server to use result from previous antispam check. Eg. by using custom spam rule "If X-Spam-Status email header contains substring DNSBL_BL_SPAMCOP_NET" you can add spam score based on a result from previous server.
My question to the community is this: It seems that Mailscanner does not append an "X-Spam-Flag: YES" to spam mail, but only sets the X-Spam-Status header. How do I configure Mailscanner or Spamassassin to set the X-Spam-Flag: to messages?
