送别信用英语怎么说

送别信，英语叫做"farewell letter"。来源是拉丁文的"vale"，意思是"再见"。
例句：
Dear John, it is with a heavy heart that I write this farewell letter to you. 我亲爱的约翰，写这封送别信对我来说是极其痛苦的。
Please accept this farewell letter as my formal resignation from the company. 请接受这封送别信作为我正式辞职的申请。
In this farewell letter, I just want to say thank you for everything you have done for me. 在这封送别信里，我只想说声谢谢你为我做的一切。