Recently started getting "mail could not be received at this time" error.

I recently started getting "mail could not be received at this time" error.The rest of the message reads: "The server for account xxxx returned the error: Logon failure: unknown user name or bad password. Your username/password or security settings may be incorrect. Would you like to retry entering your password?

All of my credentials are correct and when I enter the information it will connect for a few seconds but then ask me to enter credentials over and over. If I choose "no" it disconnects my session.

I've tried deleting the account and rebuilding, restarting my computer, and deleting my keychain. Nothing seems to work.

Thanks for any help!