英语书信最后署名时的best wishes两个单词的首字母是都大写还是只是best大写?

best 的B 大写 ,这是整个格式：
Dec.29th,2008
Dear XX,
How are you doing these days?
I am writing to tell you that I'm going to take the TOEFL examination. You know it’s a little difficult for our Chinese students and this is the first time that I take this kind of examination. So I don't know what I should do for making preparations. I want to ask you if you can give me some idea about this examination and give me some suggestions on which reference books I should buy.
I’m looking forward to your letter. Thank you very much!
Best wishes!
Yours,
XX