Unable to login to Microsoft 365 account via Outlook Application


for Microsoft 365

Q. I am unable to login to Microsoft 365 via Outlook. Please let me know how to resolve this issue.

A. The solution may differ depending on if all users are experiencing login issues or if only some users are experiencing login issues.


If all users are experiencing login issues:Please try the following methods in the order of 1.  2. 3. 4. → 5.

If only some users are experiencing login issues:Please try the following methods in the order of 5. → 4. → 3. → 2. → 1. 


Method 1.

 Check if the Domain that the user belongs has the correct DNS record registered; you should be looking for the record with the hostname auto-discover.
 If there are different DNS Servers for internal and external use, please check that the record has been configured correctly on both sides.




Method 2.

 If your company uses a URL Filtering whitelist service or firewall, please ensure that the URL of HENNGE Access Control service has been added to the whitelist.




Method 3.

 Try logging in with newly created users.
 If the newly created users can log in without issue while existing users cannot, it is highly likely that there are misconfigured parameters in the HENNGE Access Control environment. Please do not hesitate to contact HENNGE Support.



Method 4.

 If you are using Outlook2016 and have enabled the WS-Trust authentication method on the Exchange Online platform, please check if the global IP address information has been transmitted correctly to the HENNGE Access Control service.
※WS-Trust Authentication Log is not displayed on the HENNGE Access Control Admin Console. Please contact HENNGE Support to check this information.




Method 5.

 Please refer to the official Microsoft article "Federated users can't connect to an Exchange Online mailbox" below to troubleshoot Microsoft 365 login issues.


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