>From: Andy Smith <a.sm...@ldexgroup.co.uk> >Sent: Monday, March 13, 2017 11:49 AM >To: users@spamassassin.apache.org >Subject: what is triggering NO_DNS_FOR_FROM
>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. I have never seen this rule in SA because I reject these senders at the postfix MTA level before SA. I recommend doing this at the MTA level so the senders get a good bounce message that they can Google themselves and hopefully figure out their own problem before having to contact you. # grep NO_DNS_FOR_FROM /var/lib/spamassassin/3.004001/updates_spamassassin_org/* 20_net_tests.cf:header NO_DNS_FOR_FROM eval:check_dns_sender() 20_net_tests.cf:describe NO_DNS_FOR_FROM Envelope sender has no MX or A DNS records Dave
