Apple Imessage always opens itself.

1. Open the main screen of Apple's mobile phone, then click Settings-Info -iMessage, and drag the slider to the right, which means it is turned on. Touch "Receiving Method" to set the contact address of iPhone and enter the correct Apple ID.

2. After opening the iMessage service, enter the SMS interface and enter the SMS content. If the other party also opens iMessage, the mobile phone will be automatically converted into iMessage mode to send, and the content will be displayed in blue.

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Settings-Information -imessage, drag the slider to the left and close iMessage.