To do that though, you would need a foolproof, programatic way of getting an MTA to recognise a Mailwasher forgery and seperately handle it. Has anyone done this yet for any popular MTA's ? It's one thing for a human to be able to look at the headers and spot them reliably, but another for it to be automated. (Think spam filtering - FP's and FN's etc) The overhead would need to be pretty low too, since mailservers have a hard enough time filtering junk as it is...
When I was using Spamassassin I had a 100% full proof way of stopping people doing it (it seems also different versions of Mailwasher did it slightly different as well) But as I'm not using Spamassassin anymore.. then I can't find an easy way of doing it (yes I could write a simple milter to do it) Thanks Craig