$5 says that you would pass the check that Phil is suggesting. Take your IP address and do a reverse lookup on it. Then take what is returned and do a forward lookup. Do you get the original IP address? If so, Phil would accept your email. Your (additional) forward mapping from your own domain plays no part.
Exactly. Much in the same way you do not need multiple PTR records for virtual hosting/email. As long as the IP resolves to a host and that forward matches back to the IP. That identifies the host to the world at large. I don't care what domains or other services you are hosting on that single address, you can have as many forward domains pointing to it as you want.
So why doesn't the forward and reverse match on the Spam emails? Sure the people who look after those ranges should be following the RFCs as well?
While I know this isn't going to solve any spam issue (hell i was getting spam from 'correctly' configured dynamic dsl ranges in brasil at the time) and it is informational, but it's more along the lines of letting the world know that a competent admin is in charge of that server and they're doing all they can to be be 'a good internet citizen' much like spf isn't going to stop spam, but it helps to identify whether mail is coming from the right place or not. just to be clear - we are not currently blocking _anyone_ with no reverse PTR or non-matching PTR/Forwards. It just would be nice to be able to reject up front in the SMTP conversation with a simple test rather than going through the full AV/Anti-spam weighting system, This was just my monday morning rant since nznog has been quiet for a while, but it's generated some interest. There's just such an issue with the volume of spam at the moment, that if we started making information stuff mandatory i think it would make things a lot easier to manage. Much like a having a driving test before you take a car on the pulic roads, maybe there should be some sort of test before you can put a host on the internet. Phil