Outlook Modern Auth not working

Frequent Contributor

I am still being affected by this and I have a mix of users with the reg key and without




We are a 300 person Firm all working remote and the last thing I need is for Outlook to act all screwy.

Has anyone fixed this?  is this a bug?  Has Microsoft stated what the actual fix for this is?

WIndows Build 1903 18362.657: 

Outlook for O365 16.0.11929.20586


Just to recap I have user with and without the reg key in the post above and were still having the issue.

Has anyone solved this?


4 Replies

@Christian Taveras Had the same issue.   WVD/O365/FSLogix.  Fix was a combination of applying the two keys (DisableAADWAM and DisableADALatopWAMOverride) and disabling using the ODCF container for Outlook licensing and personalization. When it's working, the user will get a login prompt with a long character string, replace string with the username and authenticate.  Been stable since applying those fixes.

@Christian Taveras 




- do you run cloud only authentication or federated authentication?

- do you have AAD joined or hybrid joined clients?

- is OWA working / Browser / and or the other MS apps - Word/PowerPoint etc `? 


Would be great if you can post at least parts of the 


key...maybe just the keys, without any user identity values.


Just a few ideas what to look for: 


  • Setting DisableADALaTopWAMOverride becomes a problem for example with "older" Win 10 builds aka 1809 and with Outlook OfficeProPlus 1908 and newer ... if AAD hybrid joined .. have not tested with Win 10 1903..or the combination you posted...
  • Any error messages in the Windows 10 - Event Viewer - Application and Services Logs / Microsoft / Windows / AAD?
  • Have you tried with a new OL profile?
    • Maybe any on-prem resource mapped?
  • Anything broken with Autodiscover - Fiddler usually helps here
  • Tried Microsoft Support and Recovery Assistant - https://support.office.com/en-us/article/Resolve-Outlook-for-Windows-issues-with-automated-troublesh... ?
  • Any conditional access policy set for Exchange Online? For example, which blocks basic authN or modern authN clients... Outlook will show a nice  Password Required message in this case.. while browers still might work... 
  • Have you tried to clear the Windows Credential Cache?




Anything broken with Autodiscover - Fiddler usually helps here

Just wanted to throw out there that Fiddler is probably not the best way to test AutoDiscover. 

I would recommend to use either the builtin Outlook Autoconfiguration Test and the Microsoft Remote Connectivity Analyzer (particularly the Outlook Connectivity test and the Exchange Online Custom Domain DNS Connectivity Test).

The Remote-Analysis site cannot test your on-premise DNS, or check your Active Directory for an SCP record that might be getting in the way - neither would Fiddler.

However, the Outlook Autoconfiguration Test DOES test these on-premise problems as well.


Note: Opening the Autoconfiguration test requires Outlook to already be open, but if you are having trouble configuring the email account, you may not be able to get far enough to try running the tool.

Protip: you can open Outlook into an empty profile with no email by runningOutlook.exe /PIM NoMailThis will provision a new profile "NoMail" to use Outlook as a "Personal Information Manager" (PIM) ...


Also, I don't think the link I provided for the AutoConfigure Test mentions it, but I would recommend Disabling GuessSmart at first while you troubleshoot, and only re-enable it if the Outlook Login Prompts are acting different than your AutoDiscover tests



I don't know WHY but these TechCommunity forums insist on Mangling messages I post. 

Here are the links again


Outlook Autodiscover Test - https://help.mgcld.com/hc/en-us/articles/360025587513-Use-Outlook-to-Test-AutoConfigure-aka-Autodisc...

Microsoft Remote Connectivity Analyzer - https://testconnectivity.microsoft.com/

 - Outlook Connectivity Test - https://testconnectivity.microsoft.com/tests/Ola/input 

 - Exchange Online Custom Domain DNS Connectivity Test - https://testconnectivity.microsoft.com/tests/O365ExchangeDns/input 


Outlook PIM Instructions - https://support.microsoft.com/en-gb/office/use-outlook-without-an-email-account-477a1fc3-4423-4156-b...


and an image of disabling GuessSmart while testing