How does iPhone iOS6 switch SMS to imessage?

When the iPhone sends a short message, the content is marked in blue, indicating that the short message content is being sent in the form of iMessage. If the content is marked in green, it means that it is sent by ordinary SMS.

Only when both iPhone devices turn on the iMessage function can they send and receive iMessage information to each other. After opening the iMessage service, enter the SMS interface and enter the SMS content. If the other party also turns on iMessage, the phone will automatically switch to iMessage mode to send, and the content will be displayed in blue.

If it is sent by iMessage, it is necessary to ensure that the mobile phone is in a networked state, and so is the receiver.