On Wed, 18 Dec 2019, Brian via mailop wrote:
I never had any significant deliverability issues with my personal low
volume email server before, which I have been running for several years
following pretty much all the well-known recommendations and standards.
Two months ago I decided to take some time to setup IPv6 using a new
/64 I got from my ISP and update all the records to use ::1 in addition
to my old v4. After fixing some minor problems I was able to both
receive and submit emails using my new IPv6 address. For what I can see
on my logs, Gmail seem to prefer v6 when delivering emails to my
server, but for some reason when my server uses v6 to deliver emails
their milters mark them as spam (except of course when I send test
emails to my 15 years old personal gmail account... *sigh*)
You say that you use ::1 in addition to your IPv4 address.
Shouldn't ::1 be in addition to 127.0.0.1 and
one of your new /64 addresses in addition to your IPv4 ?
My question is: why Gmail is OK with my old v4 but at the same time
doesn't trust my new v6 when they have all the information available to
verify that both sources are in fact from the same origin?
Can I presume that this is MTA -> MTA, not mail submission (which will
leave gmail via your own gmail account) ?
Do you use a client certificate (in the TLS handshake ?) so that gmail
knows it is really you ?
What information does GMail have to determine that the two sources are the
same and how quickly could they put it all together to prove that that
deduction is trustworthy ?
*Should* they even do this ? You presumably wouldn't want a visitor
to your /64 network to have the same reputation as your mailserver,
so why should they share reputation between your IPv4 and Ipv6 ?
If I understand correctly GMail can even give different trust levels to
different apps on the same phone !
I suspect that the simple answer is that GMail has not established that
the two sources are in fact the same, and your IPv6 source, being new,
has no positive reputation.
--
Andrew C. Aitchison Kendal, UK
and...@aitchison.me.uk
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