A successful letter, that is a message from one person or organization to another, will achieve what the sender intends it to, or hopes it will, achieve.
Successful people are fanatical. It begins with the letter F.
A successful person is notable. A successful person is noteworthy.
That could be "sure"
unsuccessful
ACHIEVERS
Letter
Pot.
achievers
A "coup," used figuratively, can refer to a successful action.
· satisfying · successful
Well usually, you get a phone call if you're through, if not, you receive a letter. Usually by the end of March. They will contact you if your application is successful just before the audition process. They will send you a letter to confirm you are successful.
The show will send you a letter to confirm if you are successful.