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July 26, 2022

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Tenant Trusted ARC Sealers for Email Authentication

Exchange Online, Microsoft 365, Microsoft 365 Experts

From Microsoft Corporation
Technical Bulletin MC390410 · Published Jun 9, 2022

Message Summary

Authenticated Received Chain (ARC) is an email authentication mechanism that helps preserve authentication results across intermediaries. Email authentication mechanisms like SPF, DKIM, DMARC are used to verify the senders of emails for the safety of mail recipients, but some legitimate services may make changes to the email between the send and receipt. This intervention from legitimate services may accidentally cause the message to fail email authentication at subsequent hops. 

The ARC trusted sealers feature lets admins add trusted intermediaries in the Microsoft 365 Defender portal. This allows Microsoft to honor ARC signatures from your list of trusted intermediaries, to help authenticate the message.

This message is associated with Microsoft 365 Roadmap ID 85684

When this will happen:

Tenant Trusted ARC Sealer support will begin to roll out in Microsoft 365 Defender in early June and is expected to be completed by early July.

How this will affect your organization:

If you have had third-party service before Office 365 that modifies the email content and supports ARC, administrators can add these services as a trusted ARC sealers for your tenant. This will help messages pass email authentication checks and prevent these messages from being treated as spoof due to authentication failures.

As we are rolling out the new Email Authentication Settings page gradually, we are also moving DKIM to the DKIM tab in the Email Authentication Settings page.

During the migration, you may see two entries of the DKIM page.

What you need to do to prepare:

Identify any third-parties your organization has located before email is delivered to your Office 365 tenant and also modify content. Check if this service supports ARC and add the ARC sealer to your tenants ARC Sealer trusted domains.

Learn More: 

Additional information

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TECHNICAL BULLETIN END

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ABOUT US: QuixTec, LLC is a U.S. certified Veteran Owned, modern DevOps organization with experience in a plethora of IT Software Languages.  As a Microsoft Partner, we specialize in Discounted Microsoft Software Licensing, Microsoft SharePoint, Microsoft365 and HTML5 technologies for small to enterprise-sized organizations. Our dedication to IT excellence is evidenced through our PECB ISO Certification training center. The only PECB ISO authorized center in Washington State. QuixTec, implements and provides training for upcoming open-source digital marketing services that are taking the industry by storm. This solution, used by over 100,000 businesses, provides enterprise level marketing capabilities at startup rates. The founder, Richard, has 30 years of experience working with several notable companies that include World Vision, Expedia, Microsoft, Levi Strauss, NASA, Boeing Aerospace, Los Alamos National Laboratory, and the U.S. Air Force, to name a few.  QuixTec is in the Seattle area. Phone today for a free consultation and project estimate.

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