Hotmail/Outlook/Microsoft Email Switches to IPv6, Causing Email Failures

Peter Beckman beckman at
Thu Oct 27 23:12:08 UTC 2022

At Oct 24 21:06:13 UTC, after years of being IPv4-only, Microsoft Hotmail
published two IPv6 records for the MX record.

Great! Progress! Hurrah!

Except that one hour later, Oct 24 22:00:57 UTC, our IPv6 address was
blocked, after just 9 emails sent, as "spam."

Prior to this date, as far back as our logs go, we have had ZERO issue with
the almost 700,000 emails sent and accepted by Hotmail users since May 29,

So I visited the trusty Smart Network Data Service and Junk Mail Reporting
Program to try to troubleshoot. Except that these two services are still
IPv4-only, so I cannot even attempt to try to self-troubleshoot why
Microsoft is blocking email via IPv6.

I have opened a support ticket, but I figured I would see if anyone here
has seend or heard or had this issue, or if any Microsoft lurkers might see
this and investigate. Support request number: SR1543766049

I have not been able to find any mention in Google or elsewhere of the
planned switch to enable IPv6 for Hotmail, nor any updated way to register
with Microsoft with IPv6 address space.

Yes, we sign with DKIM and have up-to-date SPF records with both IPv4 and
IPv6 addresses. Google seems to have no issue here.

Thanks All

Peter Beckman                                                  Internet Guy
beckman at                      

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