Dear First Name, (or Mr./Ms. Last Name)
熟的用Dear 名字,不熟用Mr./Ms. 姓,自来熟/装熟用前者.
Thank you for holding my birthday party and singing the song. I really like the ...(生日礼物) you gave me.
I appreciate all the things you've done for me. They are invaluable to me.
Again, thank you so much. I sincerely appreciate your generosity.
Best Regards,
名字