Gmail (thus Nanog) rejecting ipv6 email from poorly configured senders

Sun Apr 3 01:29:10 UTC 2022

It appears that Niels Bakker <niels=nanog at bakker.net> said:
>I also run my own mail server. I had to firewall off Google's MXes for 
>this exact reason: silent and not-so-silent email rejection when 
>offered over IPv6.

I run my own mail server and have no trouble at all delivering mail to Gmail over IPv6.
I do have SPF, DKIM, DNSSEC and DANE on my mail servers.  My DMARC policy is p=none.
If it matters, the MTA is a heavily hacked version of qmail.

While I believe that Gmail rejects some people's mail, every time when
I have looked in detail, I have found that their mail authentication
isn't working properly. I'd suggest starting there.

R's,
John