This new gem is from the SMTP Gmail FAQ at https://support.google.com/mail/answer/81126?hl=en

(Fun note: they call it the “Bulk Senders Guidelines”… hence apparently anyone running their own personal mail server falls in that category…)

“Additional guidelines for IPv6

• The sending IP must have a PTR record (i.e., a reverse DNS of the sending IP) and it should match the IP obtained via the forward DNS resolution of the hostname specified in the PTR record. Otherwise, mail will be marked as spam or possibly rejected.
• The sending domain should pass either SPF check or DKIM check. Otherwise, mail might be marked as spam.”

I happen to be running my own mail server, and I happen to also be IPv6-connected, and finally I happen to be lacking a reverse DNS delegation for IPv6 because my ISP (Free) didn’t yet bother providing me with one.

I’m happier than most as my mail is sent through the eu.org server, which happens to get its mail accepted by Gmail. But it ends up tagged as “spam”.

I’m not the only one in France. OVH is reported as having the same problem.

So what are my points?

• obviously, my ISP should provide me with a correctly delegated IPv6 reverse… at some point, of course the sooner would be the better.
• but, as has been determined for over 15 years now with IPv4, refusing mail based on a lacking reverse delegation is counter-productive… since spammers statistically tend to send spam from hosts with a reverse more often than legitimate users!
• so measures like the above end up bothering legitimate users more than spammers.

So I hope Google will step back on this one, whether or not the reverse problem gets fixed.