Not sure if this helps, but Gmail requires forward and reverse DNS for
IPv6 to match.
Like this (example is from our own setup):
;; ANSWER SECTION:
e.1.7.0.0.0.0.0.0.0.0.0.0.0.0.0.a.1.e.7.0.0.4.f.1.1.1.0.1.0.a.2.ip6.arpa.
3379 IN PTR mail-db8eur05on2071e.outbound.protection.outlook.com.
;; A
Hi,
At around October 24th, mail from MS365 could no longer be delivered to
an open source MTA that I run for personal use [1].
The author of the software was able to fix it on his end.
However, I would still like to share this matter on this list. Perhaps
folks, especially from Microsoft, a
