Is it valid to change the validity period after SMS is sent?

Here's the thing. Sometimes when we send a text message, the other party's mobile phone is working, and the text message is sent directly to the other party's mobile phone; But sometimes, the other party's mobile phone is turned off, or there is no signal, or it is overdue, but it may come back in a few days. In this case, the validity period of the short message will be used. What he means is that the message will be cancelled automatically if the validity period of the message is exceeded from the time the message is sent to the other party. For example, the one who turned off the phone means that if the message is valid for one day, the other party will turn off the phone for half a day and will receive the message as soon as it is turned on after half a day. If he shuts down for two days, the message will be invalid after one day, and he will not receive the message.

In fact, it can also be understood that the process of texting is not directly from the mobile phone to the other party's mobile phone, but from the mobile phone to the mobile server to the other party's mobile phone. The validity period is the time stored on the mobile server. After the expiration date, like a dish, the short message will deteriorate and the server will not send it out.