[PeterisP]

There are very many cases in which both a 21st century and 18th century person would agree that it's reasonable for an officer with a search warrant to read through a box of letters without the accused recipient's consent; conspiracies to commit fraud justify reading your archive of business correspondence and using it as evidence in court; murders done for relationship reasons justify reading your archive of love letters and using them as evidence in court.

[UncleEntity]

It says so right in the 4th amendment "...and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

A warrant to search "your archive of business correspondence" or "your archive of love letters" is fine, reading those things while serving a warrant for your neighbors' stolen cat, Fluffy, not so much.

[Terr_]

> A warrant to search "your archive of business correspondence" or "your archive of love letters" is fine

But that's not what qwerty456127 proposed. They proposed an "absolute" right to secrecy of all correspondence.

In other words, you could catch a murderer covered in blood and you would be impossible to ever get legal permission to open the sealed envelope marked "Payment For The Job" that was in their back-pocket.