On Oct 28, 2016, at 6:04 PM, Karl Auer <kauer@biplane.com.au> wrote:
1b) anti spam filters believe in the magic of checking forward/reverse match.
Someone in this thread said that only malware-infested end-users are behind IP addresses with no reverse lookup. Well - no. As long as we keep telling anyone who isn't running a full-bore commercial network to "consume, be silent, die", we are holding everyone back, including ourselves.
If you send mail over IPv6 from an address with no reverse DNS you will see quite a lot of this sort of thing: 550 5.7.1 [*] Our system has detected that this message 5.7.1 does not meet IPv6 sending guidelines regarding PTR records and 5.7.1 authentication. Please review 5.7.1 https://support.google.com/mail/?p=ipv6_authentication_error for more 5.7.1 information.
It's fine to use no-reverse-lookup as a component of a spamminess score. It's not OK to use it as proof of spamminess.
People running large mailservers made that decision some time ago. Disagreeing with them won't make them accept your email. Cheers, Steve