I have had similar problems with Outlook Express and after
numerous attempts, I just deleted my account info
and re-did the whole thing again, starting with
setting up the incoming and outgoing mail.
Mine is SMTP.q.com and Mail.q.com
so I just go through the whole thing again
checking off the correct boxes, such as
My Server needs authentication
make sure the numbers are correct
for incoming and for the outgoing mail.
If at first you don't succeed, try try
again.