Hi ,
Before going further, please make sure you have upgraded your Outlook to the latest version.
What's the type of your account? POP, IMAP or Exchange?
In order to confirm if the issue is related to your Outlook for mac client, please try to log in to your webmail and see if your email account can work normally. It is also suggested for you to remove your email account on the Outlook client and reconfigure
them manually to see if the issue continues.
According to my research, problems with the password cache may cause issues like this. Please check the steps below and see if it works:
- Go to KeyChain Access.
- Check the option Login under Keychains and All items under category.
- Type your email address in the search box to find the information related to your email account.

- Delete the information related to your email account(Right click and select Delete"...")
- Restart your Outlook and log in to your email account.
Hope this can be helpful.
Regards,
Jeff Yang
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