I'll send the original to you by post.

我将把原件邮寄给你。

《牛津词典》

The vase was quite fragile so we had to wrap it in soft material before we send it by post.

这个花瓶很易碎，所以我们在邮寄前必须用软材料把它包起来。

youdao

You call it an "empty envelope" to emphasize that it should eventually contain a "letter" (perhaps a business letter) before you can send it by "post".

称其为“空envelope”是为了强调在通过“投递”发出它之前，它最终应该包含一封“信”(也许是商业信)。

youdao

He will send it to you by separate post (invoice enclosed) and was delighted to know you are also a lover of Charles Lamb.

NPR: Part One

It uses the post office to send clothes by air to the farthest-flung corners of the vast, icy, sparsely populated country.

ECONOMIST: Selling clothes online in Russia

All this week BBC Radio Bristol has been out and about collecting jokes from listeners across the patch, and the local newspaper, Bristol Evening Post, has been helping too by asking readers to send in their funnies.

BBC: Bristol - Share your joke with Comic Relief