I have the following DNS records set up for my mailserver (obfuscated Domain and IPs):
mydomain.net. 86400 IN A 109.83.50.87
mydomain.net. 86400 IN AAAA 2a00:5080:7:13::1
mydomain.net. 86400 IN MX 10 mail.mydomain.net.
mydomain.net. 86400 IN TXT "v=spf1 mx -all"
mail.mydomain.net. 86400 IN A 109.83.50.87
mail.mydomain.net. 86400 IN AAAA 2a00:5080:7:13::1
This setup passes any SPF verification tool I could find on the net.
However, if I try to send mail to a gmail account and the server decides to connect via IPv6 to the receiving Google SMTP, the message gets rejected with this bounce:
<receiver@gmail.com>: host gmail-smtp-in.l.google.com[2a00:1450:4001:c02::1b]
said: 550-5.7.1 [2a00:5080:7:13::1 16] The sender does not meet basic
ipv6 550-5.7.1 sending guidelines of authentication and rdns resolution of
sending 550-5.7.1 ip. Please review 550 5.7.1
https://support.google.com/mail/answer/81126for more information.
o6si5388522eea.99 - gsmtp (in reply to end of DATA command)
I suspect that something is wrong with my SPF records, but what? What else might be the cause for this?
I haven't tried setting the authorized IPs with 'ip4:xxxx.xxxx…' and 'ip6:xxxx:xxx…' instead of 'mx' yet, but I don't like that way.
Best Answer
Looks like your ipv6 sending address doesn't have PTR record. According to google support page: