> Is there some reason the Message-ID won't work as a unique > identifier? >
It's about compliance tracking and tagging for specific things. > You can use a policy server to insert a header based on > envelope information. > http://www.postfix.org/SMTPD_POLICY_README.html > > If your header must be based on the message content, you'll > need a milter or content_filter. > Indeed. We are hooking into the content_filter as we speak. We do some analytics on the email message and need to append and track content specific hit ratios for specific messages. Basically, think of putting a spam score into a message, but instead of checking for spam, we are checking to see if the incoming message violates specific guidelines. I know it might sound a little trivial as we could just as easily develop some type of database, but since all out email already goes to a compliance archive, we want to keep intact what the hit ratio was for that specific message based upon that point in time without having to worry about keeping some type of mapping in place. (that's the slightly longer reason).
