iMessage is great way to send and receive text and multimedia images with any iPhone, iPod touch, or iPad running iOS 5 or higher, as well as any Mac running OS X Mountain Lion. Along with receiving iMessages at your phone number on the iPhone, you can receive iMessages at your Apple ID email address on iOS and OS X as well. But what if you've got more than one email address and you want to be able to use all of them with iMessage? Follow along and we'll show you how!
Before you can start using an email address for iMessage, however, you'll need to make sure it's not an existing Apple ID. If your email addresses are @icloud.com, @me.com, or @mac.com your email address is automatically an Apple ID. If you have an iTunes account, the email address associated with that, and with FaceTime, are also automatically Apple IDs.
You can only have one Apple ID linked to iMessage account at a time. However, if you have additional, non-Apple ID email addresses you'd like to use with iMessage, such as Gmail, Yahoo, or Hotmail accounts that aren't connected as an Apple ID, you can set those up.
That's it. You'll receive an email asking you to confirm you have access to the entered email account. Once you do that you're ready to start sending iMessages from the newly added address!
If you're having issues getting iMessage to activate, get more help at the iMore forums, and for more tips, check out: