Is the message time envelope true?

A time envelope is a letter that you write down what you want to say to yourself or others at a certain time and then send it to yourself or others at a certain time. This is a true letter, but it has been forgotten for too long.

Envelope generally refers to a kind of bag-like packaging that people use to send letters and keep the contents of letters confidential. Envelopes are usually made into rectangular paper bags It also refers to the envelope basin, the book "Envelope" published by Yilin Publishing House, and Trojan horse envelopes, such as QQ envelopes.