Outlook Desktop (Windows) stuck in a loop asking for credentials on launch after adding Exchange accounts hosted on OVHCloud

Luc René de Cotret 0 Reputation points
2024-05-29T15:19:07.8566667+00:00

I'm having issues with the Outlook installation on my Windows 10 work PC with email accounts added as Exchange accounts (Exchange 2016 hosted by OVHCloud, not on Microsoft 365). Up until recently, I had no issues whatsoever using these Exchange accounts on the Outlook client installed with the Microsoft 365 for Business Suite. I just had to set the ExcludeExplicitO365EndPoint registry flag to 1 to ensure Outlook used the actual server designated in Autodiscovery instead of Microsoft 365 which also makes use of our company domain (but we don't use the emails there).

Since mid-February, completely out of the blue, all my work email accounts disconnected (as I was using them, in the middle of the day!) and restarting Outlook left me with an infinite credential prompt to login to Exchange, which prompts an error if I cancel out of it:

Capture d’écran 2024-05-29 104848

Error

I am 100% sure the credentials are correct, as these have been working for over a year on this very client, work on OVH's webmail, work when the email is configured as IMAP, and work on other colleague's PCs. Mine is the only one exhibiting this issue, and nothing I have tried will fix it.

As a last resort, I flushed the entire Outlook profile and re-added all the email addresses as IMAP, which causes a number of difficulties as I no longer have access to Exchange-specific features like shared calendars and contacts. Which I critically need in order to carry out my tasks. I can consult these using the web mail, but can't export from that (2016 OWA doesn't have that feature)

I routinely try to add ONE Exchange account as a test to see if the issue resolved in the meantime, but to no avail, as soon as I add ANY Exchange account not hosted in Office 365, Outlook becomes unlaunchable with the problem described above, leaving me with no other option than to remove the account from the Control Panel (which also prompts to connect to Exchange?).

Capture d’écran 2024-05-29 105317

Although the process of adding the Exchange account goes through correctly (I'm prompted to accept a certificate which confirms that it's contacting the server at OVH and not Microsoft, and successfully goes through the process of adding the email account), it looks like Outlook is also still trying to connect to some Exchange service on Microsoft 365 on the side, which fails, naturally, as that's not where the email server is. I don't know how to circumvent this and I have tried so, SO many things already, nothing works.

It's been fine for over a year, it's STILL fine for all my colleagues, it's just my particular installation that is cursed beyond imagining.

I've asked for support in the Microsoft Outlook community forum (link below) but I was redirected to this community instead by the Microsoft Agent who reviewed my question, you can refer to this post for the in-depth breakdown of everything I've tried to fix this issue

https://answers.microsoft.com/en-us/outlook_com/forum/all/outlook-365-desktop-fails-to-start-if-on-premise/0eeaa025-8524-4eee-ab25-430e401b6908

Please assist!

Microsoft 365
Microsoft 365
Formerly Office 365, is a line of subscription services offered by Microsoft which adds to and includes the Microsoft Office product line.
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Exchange Server
Exchange Server
A family of Microsoft client/server messaging and collaboration software.
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Outlook
Outlook
A family of Microsoft email and calendar products.
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  1. Mike Hu-MSFT 2,015 Reputation points Microsoft Vendor
    2024-05-30T08:47:46.33+00:00

    Hi,

    Welcome to the Microsoft forum.

    What I have to tell you is that this problem is very difficult to be solved and I will do my best to offer you some solutions that might be helpful.

    I noticed you've tried clearing Outlook credentials from the credential manager, starting outlook in safe mode, etc. Based on my personal experience, you can also try to do the following:

    • Force Outlook to use Modern Authentication, refer to: Outlook prompts for password when Modern Authentication is enabled - Outlook | Microsoft Learn.
    • Clear out any cached files that Outlook has stored. To do this, you can navigate to C:\Users<YourUsername>\AppData\Local\Microsoft\Outlook  and C:\Users<YourUsername>\AppData\Roaming\Microsoft\Outlook  and delete any files related to your problematic email accounts.
    • Update your Windows 10 System.
    • Update to the latest outlook version.
    • First start Outlook without an active network (wired or wireless) and then connect to the network. This way maybe, Outlook can connect without asking for a user and password.

    And maybe you can find some useful information in this link: Why does Outlook keep prompting for password | Microsoft Learn

    I hope this helps.Please feel free to contact me for any updates.