Gmail (thus Nanog) rejecting ipv6 email

Mon Apr 4 14:39:15 UTC 2022

Hello,

On Sun, Apr 03, 2022 at 07:44:59PM -0500, Andy Ringsmuth wrote:
> I’m running into this with clients for whom we do web site work.
> Mail not being delivered to Gmail accounts. No bounceback, not
> being delayed, not marked as spam, just black-holed for no
> discernible reason. Like, clients losing money because sales leads
> never make it to them.

Over on mailop a Google employee said that gmail never silently
discards email, that mail will always be delivered somewhere or else
rejected at SMTP time, and that the only exception is that GAFYD
customers (and similar) can set up rules themselves to delete email
under some circumstances.

I too occasionally experience customers saying their invoices and
payment reminders were silently discarded by gmail, so I don't know
who to believe.

As regards the topic at hand, gmail does seem to go through phases
of not accepting our email. While they certainly are tighter on IPv6
and absolutely require SPF, DKIM, DMARC there, other than that I
haven't seen v6 be any different to v4 and just swallow it. I know
others prefer to only deliver to them over v4.

Thanks,
Andy