Dear Prof He,

How are you doing these days?

I have some good news to share with you. I have just received the offer letter from University of XXXX. It's my first offer received and I am truly excited. I need to thank you for your great help during my application, especially for those times I feel confused with my future.

I am still waiting for decisions from other universities, and I will inform you if I receive good news. Thank you again! :-)

Best wishes,

XXXX