Microsoft Organizational Account Sign-In Fails When Zscaler Internet Security Is Enabled

Issue

Users are unable to authenticate to Microsoft organizational accounts when connected through Zscaler Internet Security. Authentication succeeds only when Zscaler protection is disabled.

Root Cause

Required HTTP header settings were not applied within Zscaler, causing Microsoft authentication requests to fail.

Resolution

1. Configure an HTTP Header Control policy in Zscaler.

2. Navigate to:

   • Administration

   • Resources

   • Access Control

   • HTTP Header Control

3. Create the HTTP Header Control profile as advised during troubleshooting.

4. Create or update the corresponding URL Filtering policy and attach the HTTP Header Control profile.

5. Test Microsoft authentication again with the affected user.