25 Jan
2014
25 Jan
'14
12:38 a.m.
Michael Fincham (michael) writes:
"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."
From https://support.google.com/mail/answer/81126?p=ipv6_authentication_error&rd=1#authentication
They've been doing this for a while now, but must have only been enabling it region by region at a time. Note this is only for v6. Maybe there's some del^H^H^illusion it will help with spam (fat good it did in v4). Cheers, Phil