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Newguy 123

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Office 365 migrated user continuously receiving modern auth prompt to enter password.

Hello Experts. In on-prem I have Exchange 2013 CU21, with AD2012. We use Azure AD Connect to sync our on-prem AD with Office 365, leverage Pass Through Authentication, and SSO is enabled on Azure AD Connect server. and are fully in Exchange Hybrid mode with centralized mailflow to Exchange Online. We have started migrating users from on-prem Exchange to Office 365. Users Outlook is connecting via Modern Authentication Protocol and Authn shows as Bearer* for Outlook client. I noticed that each day, 2 or 3 of our users that have been migrated get repeated (modern) authentication prompts from Outlook repeatedly. Some time clearing creds, and running Microsoft SARA tool fixes the issue, but sometimes it does not. For the time being, i have implemented the below reg key to disable modern auth on a few of these users, so Outlook uses basic authentication to connect to Office 365:

Reg Key: HKCU\SOFTWARE\Microsoft\Office\16.0\Common\Identity\EnableADAL
Value: 0

After implementing the above, Outlook no longer continuously prompts for passwords. Its strange that some users are getting this, while majority are just fine. About 2 or 3 different users that have been migrated complain of this issue daily, we have migrated about 300 of our users to Exchange Online so far.

Has anybody else encountered this issue. I'm wondering if this is an issue with Modern Auth in general, or is it related to something on the windows OS side, such as a missing update? I have tried recreated E-mail profile on local machine, reinstalled Office, clearing creds, restarting machine, removing work account from computer and then seems to be a hit or miss with any of these solutions. sometimes none of these solutions work on a few users, and the RegKey has to be implemented.

Please let me know if you have seen this issue as well, and how to resolve it permanently. Thanks in advance.
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Newguy 123


forgot to mention above....All the users that we migrated get Office click to run installed x64 bit. and are assigned an E3 license. and are on Windows 10 machines version 1803
Avatar of Vasil Michev (MVP)
What's the Office version? There was a known issue with the new WAM stack on W10 machines, as detailed here:
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Newguy 123

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