It depends on the rest of the context-- are you thanking the recipient for something specific? However, the way I usually wrap up this sort of letter is: Thank you very much for considering my application/submission/whatever, and I am looking forward to your positive response/comments/favorable decision/whatever. Sincerely yours, ('Regards' is too casual)
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.