I am in your debt for answering my letter so quickly; indeed, by return post.

您能这么快回我的信，我真是感激不尽；回信之快还真让我惊讶。

youdao

I am in your debt for answering my letter so quickly; indeed, by return post.

您能这么快回我的信，我真是感激不尽；回信之快还真让我惊讶。

youdao