Why does Classic Outlook fail to connect or prompt for credentials repeatedly?

Question

I’m using Classic Outlook, and recently it started prompting for credentials repeatedly or failing to connect to the mailbox. The account is valid, and Outlook on the web works fine with the same credentials.

Answer 1

Hi @Hanthorn Jeff

Could you please provide your Outlook version? You can check this in File > Office Account > About Outlook.

After doing some research, it can be due to the old corrupted or outdated credentials stored in Credential Manager in Windows - Microsoft Support.

You can close Outlook completely > Open Control Panel > Credential Manager:

Remove entries related to your account. Then, open Outlook and sign in again.

If the issue persists, try:

• rebuilding your .ost file: Close Outlook > Press Windows + R > Type in %LOCALAPPDATA%\Microsoft\Outlook\ > Look for your email address and delete it. Restart Outlook.
• Create an Outlook profile - Microsoft Support

Please try and let me know if it works for you.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". 

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.