Fix Microsoft Defender Quarantine Notifications Not Sent to External Tenants
Question details
The user needs to resolve an issue where external tenant addresses do not receive quarantined email release requests.
- Product
- Microsoft Defender for Office 365
- Device & OS
- not provided
- Scenario
- Configuring alert recipients to notify an external guest user about quarantined email release requests.
- Observed behavior
- Quarantine notifications are not delivered to the external tenant address, even after adding the address as a guest user and selecting it as an alert recipient.
Verify that the external email address is correctly configured as a guest user in your Azure Active Directory and ensure you have global admin or security admin privileges in your Microsoft 365 tenant before reviewing policies.
Request Assistance from Microsoft Enterprise Support
Because cross-tenant alerting involves complex enterprise security policies, the issue must be investigated by Microsoft Enterprise Support via the official Q&A forums.
Standard consumer support channels cannot investigate backend tenant policies or cross-tenant alert routing issues. Escalating the problem to the Microsoft Q&A enterprise forum is the most effective way to resolve advanced Microsoft Defender configuration errors.
Open your web browser and go to the official Microsoft Q&A portal at learn.microsoft.com/en-us/answers/.
Log into the portal using your Microsoft 365 enterprise administrator account.
Create a new question detailing your cross-tenant alert issue. Be sure to include relevant tags such as 'Microsoft Defender for Office 365' and 'Exchange Online'.
Monitor your post for responses from specialized enterprise support engineers who can investigate your backend policy behavior and quarantine notification permissions.
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Frequently Asked Questions
Why aren't external guest users receiving quarantine release alerts?
Microsoft Defender policies often restrict automated alerting to internal domains by default to prevent data leakage. Routing alerts to external tenants typically requires specific cross-tenant configurations or specialized Exchange mail flow rules.
Can I add an external email directly to the alert policy?
While the interface may allow you to add external emails or guest users to alert policies, outbound spam policies or default Exchange security rules may silently drop or block these automated notifications.
Where can I manage quarantine alert policies in Microsoft 365?
Quarantine policies and alert recipients are managed in the Microsoft 365 Defender portal under Email & Collaboration > Policies & Rules > Threat Policies.
