Straight from the proverbial horse's mouth (someone at MS), shared with
permission:
"We are migrating mailboxes from the current Hotmail/outlook.com infrastructure
over to Office 365. This means that migrated users have their mail hit
Hotmail's front end and then forwarded to Office 365 where it re-undergoes an
authentication check, but is not actually enforced. The original spam/non-spam
verdict at Hotmail is re-propagated through the system. If the message is
subsequently forwarded some other place, it will fail DMARC because Office 365
has an issue where it modifies message content when forwarding ("fixes" it up).
This behavior will be changed in the Sept/Oct time frame."
---
Anne
Anne P. Mitchell,
Attorney at Law
CEO/President
ISIPP SuretyMail Email Reputation, Accreditation & Certification
Your mail system + SuretyMail accreditation = delivered to their inbox!
Are you an ESP? Ask us about our Email Academy for YOUR Users!
http://www.SuretyMail.com/
http://www.SuretyMail.eu/
Author: Section 6 of the CAN-SPAM Act of 2003 (the Federal anti-spam law)
Member, California Bar Cyberspace Law Committee
Member, Colorado Cybersecurity Consortium
Ret. Professor of Law, Lincoln Law School of San Jose
303-731-2121 | amitch...@isipp.com | @AnnePMitchell
Facebook/AnnePMitchell | LinkedIn/in/annemitchell
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