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July 25, 2022

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Consistently block delegates or shared mailbox members from accessing protected messages in Outlook

Exchange Online, Microsoft 365 Experts

From Microsoft Corporation
Technical Bulletin: MC389620 · Published Jun 6, 2022

Message Summary

Outlook will provide consistent access control on protected emails (Protected by MIP Sensitivity labels, or RMS protected emails) for Microsoft 365 delegates and shared mailbox members. For delegates or shared mailbox members, when they have full access of the owner’s mailbox but are not allowed to read encrypted email, Outlook will have a new cmdlet setting to block the owner’s protected email access which covers ad-hoc encrypted email as well as email with protected MIP sensitivity labels.

This message is associated with Microsoft 365 Roadmap ID: 88888

When this will happen:

  • Preview: We will roll out the preview in early June
  • Standard: We will begin rolling out in early July and expect to complete by late August

How this will affect your organization:

Based on customer feedback, we are introducing new Get/Set/Remove-MailboxIRMAcess cmdlets that provide admins with more granular access control of encrypted content, including in scenarios where delegates or shared mailbox members have FullAccess to the shared mailbox

We will introduce new Get/Set/Remove cmdlets which tenant admins to use to limit delegate access to RMS messages at mailbox level.

  • Check who is blocked from accessing mailbox owner’s encrypted messages:

Get-MailboxIRMAccess -Identity <MailboxIdParameter> -User <SecurityPrincipalIdParameter>

  • Blocked a user from reading encrypted messages in a shared or delegated mailbox:

Set-MailboxIRMAccess -Identity <MalboxIdParameter> -User <SecurityPrincipalIdParameter> -AccessLevel <Block>

  • Remove a user from the block list and allowing them to read encrypted mail:

Remove-MailboxIRMAccess -Identity <MalboxIdParameter> -User <SecurityPrincipalIdParameter>

After any of the above mailbox settings are changed, the Outlook client must be restarted.

Parameter definitions:

  • -Identity: The target mailbox. You can use any value that uniquely identifies the mailbox.
  • -AccessLevel: Specifies what delegates can do with IRM-protected messages in the specified mailbox. Currently we only support “Block.”
  • -User: Specifies the delegate or shared mailbox member who is blocked from reading IRM-protected messages in the mailbox or shared mailbox. The user’s login ID must be used.

Once delegate is blocked to view the owner mailbox’s protected email, the delegate will see the following when they trying to open the protected mails

Delegated protected email experience
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Or Shared mailbox member is blocked to view the mailbox’s protected email, the login user will see the following when they trying to open the protected emails.

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What you need to do to prepare:

If you do not do any cmdlet settings, there will be no impact on your existing delegate or shared mailbox protected message reading experience. But if you choose to block some of the full access delegate or shared mailbox members to read the protected email, you could configure through the cmdlet above.

Additional information



QuixTec provides this and other technical bulletins unaltered from Microsoft. As an authorized Microsoft Partner, we ensure that all our solutions we deliver to you include the latest Microsoft updates.

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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