"registered mail" is a correct and usable phrase in written English.
It can be used whenever you are referring to a mail service requiring a signature upon delivery, as confirmation that the item has been received. For example, "I received the contract I ordered by registered mail."
A related service, registered mail, has a much smaller volume.
That meant delivering registered mail to the players' clubhouse.
If you send a letter, send it registered mail with return receipt, and keep your own copy.
We track down fax machines to send copies to six separate government offices, and send another to an attorney via registered mail.
The range of services available to the public has also grown steadily since the first supplementary postal service, registered mail, was introduced in 1855.
The day after my grandfather's appointment with Danny Thomas, the envelope containing his "Poeme in English" arrived at his house, via registered mail.
I have distinct memories of standing in the post office filling out registered mail forms since that was the only way some of the companies would accept a request to freeze a file.
Send it registered mail for added gravity and while you're at it, note that you've sent a copy of the letter to a government agency, like the Federal Trade Commission.
Many residents are asking for a regular post office, but Mr. Rosario said the Postal Service was instead considering installing a smaller center known as a contract station, which sells postage and handles registered mail.
An RIAA notice arrived in triplicate, via email, registered mail, and FedEx overnight (with print and CD versions).
Lastly, Pedrana and co-workers [ 44] found that sending surveys by registered mail cost an additional AU$1531.50 but led to a 19% increase in response rates (response rate: 86% registered mail versus 67% normal mail).
