Q: I have a third-generation iPad and I want to use FaceTime and iMessage with friends who live outside of the U.S. However, I keep getting a message that says “Not registered with iMessage” whenever I try to send to them. What does this mean? They have an iPhone. Can you help?
A: This error means that the number or e-mail address you are trying to reach is not registered with Apple’s iMessage servers.
Assuming that you are using the correct phone number or e-mail address, this could mean that they either have iMessage disabled entirely on their iPhone, they have been unable to activate iMessage properly for some reason, or if you’re using an e-mail address they simply have not added it to their iPhone. In this case, the problem would be on their end and they should go through the necessary steps to ensure that iMessage and FaceTime is properly enabled on their iPhone.
Note that when sending internationally to a phone number, you must be certain you are using the proper international phone number format, including the country code. For example, if you’re trying to send an iMessage to somebody in the UK, you would need to prefix it with +44 (the country code for the UK) followed by whatever the local number is.
Similarly, for them to call you they would need to ensure that they prefix your phone number with +1—the country code for North America. You can find a list of international country codes at countrycode.org—remember to prefix the country code with a plus sign.
Alternatively, if your friends have setup an e-mail address for FaceTime and iMessage, you can simply enter that in the address field in place of a phone number when sending iMessages, or select their e-mail address when placing a FaceTime call. To do this, they must have setup and signed in with an Apple ID for both FaceTime and iMessage and ensured that their e-mail address has been added and verified with Apple.