Go to your email providers web mail page and log into your account there. Read and delete the problem email and see if the other emails free up.

It doesn't matter how many times I open or delete the email. It still is the only message that will open or download.

Maybe, if it's a POP account, there's a corrupted popstate.dat file:

http://kb.mozillazine.org/Repeatably_downloading_the_same_messages

Help/Troubleshooting Information, click Show Folder, exit TB, delete the file.

Airmail you were right. When I went to the web provider page not the email providers page and deleted it the emails were freed. thanks