Email down again - Enter New password

I have been getting spurts of email outages with the message "Login to server imap.cox.net with user name xxxxxxx53 failed.  I am give choice to retry, enter new password or cancel.  I know the password is correct as I can log into webmail.  However today even after logging into webmail I could get to my email list.  I use Thunderbird and have used without  problems for 5 years until the past month.

Marty