If you receive an notification or error message similar to the below;

• Your email server rejected your login. Verify your user name and password for this account in Account Settings. The server responded: -ERR Logon failure: unknown user name or bad password.
• Incorrect password entered

Have you recently changed your password? 

If so, it could be that you have not yet updated the password in Outlook.

Note, the password must be setup for both incoming and outgoing settings.

Please refer to this article on how to Modify mail server settings - Outlook

App Specific Passwords (ASP)

Have you recently setup ASP?  If so, you will need to update the password in Outlook using the ASP.

Note, the password must be setup for both incoming and outgoing settings.

Please refer to this article on how to Modify mail server settings - Outlook