Hello,
We have a disgruntled customer that specifically created an email address to subscribe it to spam lists/newsletters and then they set up that email address to forward all emails to one of our support emails, creating a large amount of spam that can't really be blocked by traditional means. The original senders are, more or less, legitimate and mostly legitimate newsletters, so I wouldn't expect a spam filter to capture them.
The received emails have the original senders email address in the From Header (noreply@some_legit_company.com) which is what the blacklist is checked against, i pressume.
What i want to do is filter by the forwarders email address which can be found in the "Resent-From:" and "To:" headers.
Any idea how i can filter by these headers specifically? I think filtering by "Resent-From" would be the most reliable in this instance.