I refer to this discuess page.
https://discussions.apple.com/message/16350158#16350158
I guess I got the same problem. When I sent the mail, I got the system messenge to ask me setup up the server. However, when I setuped up my mail box's primary smtp address I got the other problem. I can't toggle "DONE" this button. It's grey out.
I wish Apple can have a fix update for this issues. It suppose not only one having this problem.

