I use a single smarthost as a hub to route all email from my network so that I can pass SPF checks on Gmail. However, although I always send through the same server, the
From address can differ. For instance, a cron job on the server
dev.mydomain.com might generate the From address
firstname.lastname@example.org. I use
/etc/aliases to redirect this cron email to my real email address. This email uses hosted Gmail, so the MX for
mydomain.com points to Gmail's servers.
However, Gmail doesn't like these
From addresses, probably because they don't exactly match the SPF record which is defined on
mydomain.com. I receive the message that
Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication.
I don't want to have to define separate SPF records that allow my one mail server to submit email for every single subdomain that I want to allow in the
From address. Instead, I'd like to allow
*@*.mydomain.com, as long as it is sent through the correct server.
2016-12-22 14:04:17 1cK3yj-0007Wz-4I <= email@example.com H=(dev.mydomain.com) [2a01:7e00::f03c:91ff:fe79:81b] P=esmtp S=586 id=E1cK3yj-0006Nxfirstname.lastname@example.org 2016-12-22 14:04:17 1cK3yj-0007Wz-4I ** email@example.com R=dnslookup T=remote_smtp X=TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128 DN="C=US,ST=California,L=Mountain View,O=Google Inc,CN=mx.google.com": SMTP error from remote mail server after end of data: host ASPMX.L.GOOGLE.com [2a00:1450:400c:c07::1a]: 550-5.7.1 [2a01:7e00::f03c:91ff:febb:7422] Our system has detected that this\n550-5.7.1 message does not meet IPv6 sending guidelines regarding PTR records\n550-5.7.1 and authentication. Please review\n550-5.7.1 https://support.google.com/mail/?p=IPv6AuthError for more information\n550 5.7.1 . p21si28305523wmb.29 - gsmtp
I am using Exim on Debian.
[Edit: It seems the cause was the reverse DNS/PTR record.]