It means that the other party did not receive the message. Why?

The reasons why the SMS was sent successfully but not received by the other party are as follows:

1. The receiver's memory is full, so just delete the redundant messages.

2. The receiver signal is poor, so it is recommended to send it to a place with good signal.

3. Congestion, packet loss or interconnection obstacles affect the processing of short message center.

4. SMS function is not enabled.