How to reset the mail app?

So I think the mail app on my MBA running 10.8.2 is glitched.

I synced a secondary @icloud.com account but entered the wrong password. I now cannot even get back into the settings to change or delete the account. Every time I try to do so, I get the infinite spinning rainbow circle, which does nothing and I would have to force close the mail app.

Sorry I'm new to OSX. What can I do to fix this problem?

Thanks!