Outlook continuous password prompt

Outlook Continuous Password Prompt Outlook

Out of the blue, an Outlook continuous password prompt appears that does not go away after entering the correct credentials. Meanwhile, Outlook is connected to Exchange and it is possible to send and receive mails. The annoying Outlook continuous password prompt stays at the top of the screen and can just be dragged to the side.


In the inquiries we received regarding this all admins stated that no changes were made to Outlook, the client PC or the internal customer network. It came from one day to another.
We checked all the obvious and some more specific possibilities on the clients which were :

Windows Credential Manager:Result : negative

  • Make sure the current password is set under Generic Credentials in the Outlook / Office entry
  • As second option delete the entry, start Outlook and and check remember password when prompted for credentials. A new entry will be created under Generic Credentials which represents the same situation like the 1st option.
  • The 3rd option was to check if there are any other entries which can give us a hint where Outlook wants to connect to. ( there wasn’t )

Autodiscover:Result : negative

  • Since users were able to send and receive mails and their Outook client was connected to Exchange successfully it could not really be an issue with Autodiscover trying to connect to a wrong server. To go for sure we set appropriate autodiscover entries in the hosts file. ( even when autodiscover was resolving correctly from the client )

Shared mailboxes – Sharepointlists – calendars within the Outlook profile:Result : negative

  • We checked if there were any items from another shared mailbox integrated in the users Outlook profile, which could cause the Outlook continuous password prompt. ( This has already been checked with the 3rd option under Windows Credential Manager but you know the devil is in the details )

Skype:Result : negative

  • Checked if Skype is configured at Startup. Some users had it some not. We made sure that there is no Skype in the background when starting Outlook. The password prompt appeared and stayed again.

Created a new profile:Result : worked out but not final solution we used

  • This worked out. The Outlook continuous password prompt disappeared. We cannot say if the password prompt reappeared again after some time. Creating a new profile for customers with many users was no option ,so this was not the final solution we suggested.

What we have noticed:

All reports to this behaviour came from users using Outlook click and go with the following build version and build numbers:

Version 1707 – Build Nr. Build 8326.2107
Version 1707 – Build Nr. 8326.2096
Version 1708 – Build Nr. 8431.2079

I cannot say if this is only limited to these versions.

After all that has been done is mentioned ( maybe it helps you in your own troubleshoot ) I’m gonna wrap it up.

We opened a call by Microsoft. After the usual log collection steps and several tests they came up with a registry key :Result : Final solution

DWORD : ExcludeExplicitO365Endpoint
Value 1

It seems the affected Outlook clients tried to connect to an Office365 endpoint as well. No one could tell us why it happened from one day ( all working fine ) to another ( Outlook continuous password prompt appeared ).

Microsoft said that Windows Updates were not responsible for this behavior. They assume that the password prompt occurs when a client accesses an O365 endpoint.

For example, when an old mailbox within the profile has not been deleted correctly and still an autodiscover request is made. When we take the fact that a new profile solves the problem without setting the registry key, this could be possible.


We had some scenarios where the users had the registry key in place already but the Outlook continuous password prompt still appeared. Outlook still wanted to connect to outlook.office365.com.
The solution was to add the following entry to the hosts file:     outlook.office365.com


It seems there is a similar issue with opening attachments where Microsoft has released an update for O365. I found this info on Stephen Wagner’s blog ( Thx Stephen ! ).

See comments to this on Technet as well : Outlook 2016 prompting for login credentials when opening any email attachments

Problems with slow autodiscover ? Read this:

Autodiscover takes long time Outlook

2 thoughts on “Outlook continuous password prompt”

  1. Out of curiosity, did your troubles begin mid/late September? Because that’s when it started spontaneously for hundreds of users here, whereas we previously never had issues and we didn’t make any changes to environment at that time either.

    1. Hello AC ,

      Exactly. The first customer reported this on the 20th of September , where he had this issue on several clients for some days already.
      I tend to believe MS has pushed out something what triggered this behavior. Aside from their statement that it is not caused by an update.
      Too many clients in different networks were affected in the same time period without undergoing any changes.


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