English help needed...?

As your tutor writes to you and calls you KT, it would be ok to write to him informally - Hi John. You can use regards if you want, or just put KT at the bottom. It's only when you write a formal letter that you would use Dear Mr Smith. You would write Mr J. Smith then his address underneath, then put the date and ref if you have one, then Dear Mr Smith. You would then finish the letter Yours sincerely. xx