I'm having a little trouble getting to grips with how Postfix's various filters + checks interact with eachother and, unfortunately, I haven't been able to dig up much to help me with my latest experiment ...
I'm trying to cut down on spam by filtering out messages from, say,
sender@yahoo.co.uk that haven't passed through a yahoo mail server.
I realise that such a technique might foul up from time to time but, for the short term at least, it would make a
big difference to me. For the moment, I'm anxious to avoid going at the problem from the other end, with long blacklists, sender address verification, etc, etc.
Anyhow, I've been playing around with various possibilities, but I'm starting to get the distinct impression that Postfix has been designed to prevent people doing silly things like this.
My question, I suppose, is whether anyone has set up their Postfix to do anything like this, or whether I'd be better trying to persuade Spamassassin to do it, maybe. I'd appreciate any pointers ... hopefully I'm not overlooking something simple.
