On Nov 26, 2014, at 6:00 PM, Frank Bulk <[email protected]> wrote:

> This afternoon I saw several log messages in our email server's logs in
> relation to emails our local business customer (who uses our ISP email
> server) was trying to send to a Microsoft Office 365 hosted domain:
> 
> "[::ffff:12.43.166.xx] Site <target domain redacted>
> (2a01:111:f400:7c0c::11) said after data sent: 554 5.7.1 Service
> unavailable, message sent over IPv6 [2607:fe28:0:4000::10] must pass SPF or
> DKIM validation (message not signed)”
> 

It is all explained here: 
http://blogs.msdn.com/b/tzink/archive/2014/10/28/support-for-anonymous-inbound-email-over-ipv6-in-office-365.aspx

Note, there are now 3 IPv6 receivers that requires DKIM or SPF for email over 
IPv6: Google, Microsoft and Linkedin. It is a M3AAWG BCP.

http://engineering.linkedin.com/email/sending-and-receiving-emails-over-ipv6
https://www.m3aawg.org/sites/maawg/files/news/M3AAWG_Inbound_IPv6_Policy_Issues-2014-09.pdf



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