Attention MDR Customers: New Case Submission Flow

As of March 18, 2025, there is an updated process flow to submit MDR-related cases. Please visit this article for details.

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Approved/Blocked Sender List does NOT accept invalid email format. As a workaround, you may do the following:

Check the email header where the email address with an invalid format is listed.
For example:
From: user@domain
On the CAS web console > Go to Advanced Threat Protection > Exchange Online Policy > Advanced Spam Protection > Approved Header Field List > Enable the approved header field list
Add the information in the Approved Header Field List.

Keywords: email address, invalid format, Approved Sender List, Blocked Sender List, Cloud App Security

Adding email address with invalid format to Approved/Blocked Sender List of Cloud App Security (CAS)

Cloud App Security For Office 365All

Last updated: 2025/05/08

Solution ID: KA-0013966

Category: Configure , Troubleshoot

This article will provide a workaround to allow/block email addresses with invalid format.

Approved/Blocked Sender List does NOT accept invalid email format. As a workaround, you may do the following:

Check the email header where the email address with an invalid format is listed.
For example:
From: user@domain
On the CAS web console > Go to Advanced Threat Protection > Exchange Online Policy > Advanced Spam Protection > Approved Header Field List > Enable the approved header field list
Add the information in the Approved Header Field List.

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