Outlook Authentication keep prompting after changing Exchange user UPN

[Curious_Kevin16]

We have an Exchange 2016 environment and are planning to move to Hybrid Exchange. We had an issue in the UPN format where we needed to change from "email address removed for privacy reasons" to email address removed for privacy reasons". sAMAccount name remain intact (domain1\user). 

After this change Outlook Desktop App users getting prompted for authentication despite entering the correct credentials. OWA is fine. Has anyone seen/was able to sort out this issue?

Thanks in advance !

Kev

[#2]

Hi @Curious_Kevin16,

you can try the following:

1. Clear Cached Credentials in Windows Credential Manager:
   Try clearing the cached credentials on the affected Outlook clients. You can do this through the Windows Credential Manager. Remove any entries related to the old UPN or Exchange server.
   Accessing Credential Manager - Microsoft Support

2. Recreate Outlook Profile:
   If the issue persists, consider recreating (remove and create) Outlook profile for the affected user. This will ensure that Outlook is configured with the latest UPN information and other settings.
   Remove a profile - Microsoft Support
   Create an Outlook profile - Microsoft Support

3. Check Autodiscover Records:

   Ensure your DNS records for autodiscover.yourdomain.com are correct and point to the Exchange server.
   Find autodiscover URL in Exchange with PowerShell - ALI TAJRAN

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