Mail Program frozen with one message open & grey

Hi, I am on mac laptop OSX 10.9.2 using Mail 7.2. I've never had any problems, but today I tried to open a "Mailer Daemon" message and it is frozen, not even open but a grey colored blank "message". I've tried:

• closing the message unsuccessfully
• Force Quitting the application (reads "Mail (not Responding)") when I do. (4 times)
• Turning off the entire computer, letting it rest and rebooting. (3 times)
• Opening up my server on the internet and deleting the offensive message "mailer daemon"
• Turning off the computer again.

So...as soon as I open mail, the grey "message" is open. I can click on the Mail Viewer window and have that come forward, but all is frozen.

Just did it again and it hasn't changed. Had to force quit again. Never before in 8 years of using the Mail application (different computers).

I'd really be so grateful for any suggestions and help. The rainbow wheel of death spins and spins. This is what I see...Grab is open to take a screen "grab".

Thank you so very much! Catherine