Vista - Windows mail will not send-User name and Password dialog box

I have read many responses posted here related to the dialog box requiring a
user and password prior to sending email from Windows Mail. I am pulling my
hair out with this same problem. I have uninstalled my Norton software and
replaced with avast. Additionally, I have removed and redone email accounts
numerous times and the dialog box keeps returning without fail. Has anyone
cracked this problem yet? Any information would be helpful.

"Brian" <Brian@xxxxxx> wrote in message
news:62B6147F-88A7-4E06-901A-84B18DEF8241@xxxxxxDid you run this progran to clean up after Norton?

<http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2005033108162039>

Did you use the standard install for avast!? If so, it may help to
uninstall it and
then do a custom install which tells it to leave out the part that scans
email.

http://www.avast.com/eng/avast_4_home.html

In Windows Mail, click on Tools, then Accounts, then your email account,
then Properties, then Servers. If there is no check mark in the box before
Remember password, click on this box and then Apply. Click on OK and
then Close.

Have you tried entering your username with no CAPITAL LETTERS?
Have you tried entering it followed by the part of your email address
starting
with @, and also without this? Have you made sure you enter the password
with CAPITAL LETTERS and lowercase letters in the correct places? Not
all email providers tell you which of these they have set the email servers
to
accept. Some even disable your email account for a few minutes after each
failure, to cause trouble for people trying to guess your password.

Have you tried connecting with the webmail connection, if your email
provider offers this, to get more of an idea what they insist on?