username and password request.

I also had this happen starting last night. It would simply keep asking for
the same info and I would get an error message in Windows mail if I did a
send/receive. It went away and has worked correctly after I went to Google
gmail and signed in. I viewed the mail. After a minute, the one I had been
trying to send in Windows mail appeared. I then logged out. Windows mail has
worked from then on.