Why does the SMS sent by Apple's mobile phone have an exclamation point?

The exclamation mark in the Apple message indicates that the message failed to be sent;

The solution is as follows:

1. Open the phone and click the "Settings" system icon.

2. Click the Info option again.

3. Turn on the "iMessage" option on the right, and turn it off and restart.

If you want to clear the exclamation mark on the message, we need to turn off the Apple phone.

5. Turn on the Apple phone later, and then click the "Info" icon.

6. Then send the unsent message.