The people who provide the best answers in this newsgroup tend
to use connection methods that make some things easier, but also
make it difficult to go back to previous messages in the thread to
see more about what your problem is.

If you're using Norton Antivirus, that happens to be one of the more
common causes for problems in Windows Mail, and even disabling
the whole antivirus program seldom helps.  You usually need to
uninstall the Norton program instead.  You often then need to run
this cleanup program to take care of what the uninstall left behind.

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

You may even need to remove your email account under Windows
Mail, then restart Windows Mail and add the account again.

If any of the messages in the Outbox can't be moved to the
Drafts folder and can't be deleted, download and install this
hotfix, with Windows Mail not running:

http://support.microsoft.com/default.aspx/kb/941090

Although it's labelled as for mail stuck in the Outbox, it also
works in other folders.The Vista SP1 update includes this
hotfix, but takes longer to install.

If this solves your problem, you may want a replacement
antivirus program that doesn't cause such problems in
Windows Mail.  Most versions of the McAfee antivirus
program and a recent version of the Trend antivirus
program are bad choices; they also cause problems in
Windows Mail.  I recommend either avast! or AVG,
either one with a custom install that tells it to leave out
the part that scans email.

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

http://free.grisoft.com/ww.download?prd=afe