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yyu018 avatar image
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yyu018 asked grimson edited

Need Advice: Exchange Hybrid - password prompt when on-prem user open online mailbox user's calendar

We have moved pilot users' mailboxes to Exchange Online. During the test, we found that on-prem user keeps on getting password prompt when try to open online mailbox user's calendar. The credential pop-up wouldn't go away even typing in the right password few times. The only way to solves this is recreate the on-prem user's Outlook profile.

As we are doing the migration in batch, it will be annoying to rebuild the Outlook profile for quite large amount of users, who used to open other's calendar to check the availability in Outlook.

Is there any solution for this or workaround? Your advice will be highly appreciated.

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KyleXu-MSFT avatar image
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KyleXu-MSFT answered KyleXu-MSFT commented

@yyu018

This phenomenon is caused by the change of Autodiscover. If you don't want to recreate Outlook profile, you could try to delete and add that user's calendar, check whether autodiscover record could updated successfully.

If this phenomenon still exist, you may need to recreate profile after migration complete.


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Hi Kyle,

Thanks for helping me again.

Do you mean our on-prem user having password prompt issue to open online user's calendar should delete/remove then add that user's calendar again? Thanks.

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Suggest you try to add calendar again. In most cases, you will need to recreate your Outlook profile.

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Any update about this thread now?

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Remove and add calendar again didn’t not work. Still have password window popped up.

Recreate profile is the only way to solve the problem at this stage. But it is painful to go through all the problematic users to recreate profile.

Do you have any alternative solution or way to speed up profile recreation? Many thanks.

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grimson avatar image
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grimson answered grimson edited

This helped me:
https://docs.microsoft.com/en-us/outlook/troubleshoot/authentication/outlook-prompt-password-modern-authentication-enabled

Outlook Client:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Exchange]
"AlwaysUseMSOAuthForAutoDiscover"=dword:00000001

This should allow an on-premises Outlook Client/mailbox to access an Shared EOL mailbox.
This will trigger a modern Authentication logon.

I tried to open other mailbox folder like inbox but that access to a specific folder did not work. Guess you have to add the whole shared mailbox in your Outlook profile.
It could be possible that this triggers the correct authentication and if you remove the full mailbox again this wil keep working and can access a folder instead of the whole mailbox.


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