This letter is too important to send by mail.

这封信太重要了，不能用邮递方式送去。

youdao

For example, it would be possible for you to send by mail train your Sunday lunch leftovers for your friend to eat for his Sunday lunch.

比如，对你来说你可以用邮政列车把你周日午餐的剩饭菜寄给你的朋友做为他周日的午餐。

youdao

He asked his mother to send it by registered mail.

他让他妈妈用挂号邮件寄。

《柯林斯英汉双解大词典》

Lawmakers in Congress wanted to make it possible to send mail all the way across the United States by land.

VOA: special.2010.04.26

She is hoping to board a plane next Sunday. "If there are no flights, even until then, I will probably have to send my luggage by mail,and then try and get a train ticket going to Madrid and then maybe try and get back to Korea via New York or via Bangkok or Hong Kong.

VOA: standard.2010.04.19

Parties in the Wilmington area that wish to register wireless microphones for event venues during this period of limited operation must send a request to OET by e-mail in accordance with the instructions provided in the Public Notice.

ENGADGET: FCC approves first white space device and database for Wilmington, NC

Okolloh, 31, created the site using Ushahidi, a free piece of software that quickly creates Web sites to which eyewitnesses of war and crisis in out-of-reach places can send news by e-mail or text and have it attached to a Google map.

FORBES: Magazine Article

"During his captivity, the Yugoslav officer will enjoy all the protections and rights accorded by the Geneva Conventions, including the right to send and receive mail, " a statement from the Pentagon said.

CNN: U.S. holding Yugoslav officer as POW