How is everything?一切都好嗎?
I hope everything is all right.我希望(你)一切都好。
How are you?你好嗎?
How are you getting along these days? I miss you very much.你近來過得如何?我十分想念你。
I was very happy to receive your letter of October 10th.我很高興收到你10月10日的.來信。
Thank you for writing to me.謝謝你給我寫信。
Your letter came into my hand yesterday.我是昨天收到你的來信的。
It's a long time since I got your last letter.我收到你的信已經很長一段時間了。
I'm sorry I took so long to reply.很報歉給你回信晚了。
I have been so busy recently that I could hardly find any time to write.我最近挺忙，未能抽出時間給你寫信。
Many thanks for the wonderful present you sent me.謝謝你寄給我那麼好的禮物。
I'm so sorry for not having written to you for such a long time.十分報歉，很久沒有給你寫信了。
英語書信結尾常常寫一些祝願、問候他人、盼回信等等話語。常用的語句有：
With best wishes.致以良好的祝願。
Please write to me as soon
How are you?
How have you been?
I hope everything is fine with you.
Hope you enjoy your day.
(或者)Here I am again.
It's me again.
郵件比較頻繁的話，直接說Good morning/afternoon就ok了。