The address of the text message received by my iphone is the email address. Is this traffic or SMS?

Your friend sent you an iMessage message instead of a traditional text message. And it is sent by Apple ID, just like MSN, an instant messaging tool that we often use. Since it is an instant messaging tool, it has nothing to do with whether you turn on flight mode or not, as long as you are online, you can use it. Therefore, iMessage infringes on the SMS revenue of operators to a certain extent, so not all operators in the world support iMessage. When you turn on edge and turn off wifi in non-flight mode, the short messages you send to your friends will take away the traffic.

When setting up the iphone, the Apple ID or your mobile phone number is usually registered with your device number on Apple's push server. When setting iphone to open iMessage, if Apple ID has been set in advance, iphone will register your mobile phone number and Apple ID at the same time, and the latter is the preferred contact method for iMessage. This is your friend's phone settings, not your phone settings.