Hi all, I have a some genuine emails getting marked with NO_DNS_FOR_FROM from one particular domain and I'd like to know exactly why. I've had a dig in the Spamassasin Dns.pm but I can't work out exactly what process_dnsbl_result is doing. What exactly does it check WRT MX and A records?
I can see that the domain in question does have A and MX records, possibly issues are that the A record doesn't match the PTR for the IP returned by the A record and that one of the MX records doesn't have a PTR. I'd be keen to know if one or both of these are the issue, and what the situation WRT RFCs on email DNS says about what are required for proper operation of email. I've already had to ask the owners of the domain to correct an issue where their sending server's A record didn't match the PTR and was triggering the RDNS_NONE rule (as detected by Exim), so if I'm going to convince them to do more modifications I'd prefer to know what I was talking about, thanks, Andy.
