It seems that spammers, in an attempt to get through mail filters, have given up even pretending that they are sending legitimate mail. Some of the subject lines I recieved today were:
Re: DZFWKYK, there came flying
and
Re: MXG, schizophrenic but also
The goal appears to be to make the subject lines difficult to write a general-purpose regular expression for. And that seems to be the only goal. Because what sane person would open an email message with a title like that?
By the way, this seems to work in most cases:
/Re: [A-Z]{2,}, [a-z]+ [a-z]+ [a-z]+/
And, if folks send legitimate email with a all-caps first word, well, they'll get a friendly reject message and can resend.
So the entire postfix rule would look like:
/^Subject: .*R[eE]: [A-Z]{2,}, [a-z]+ [a-z]+ [a-z]+/ REJECT Your message has been rejected because it looks like the latest rash of spam. If this was legitimate email, please resend with less spam-like qualities. Thanks.
Or, if you don't care about false positives, and/or don't want to alert the spammers that you're smarter than they are, just DISCARD instead of REJECT.
Have I mentioned lately how much I despise spammers?