In order to get your iMessage run under the new iOS 5 (iPhone & iPad), you need to activate this feature for the first time:
1. Go to –> Preferences –> Messages
2. Switch the button iMessage on
3. activate iMessage by confirming your Apple-ID
4. at the end you can add other addresses like email or phone numbers under which you want to receive iMessages.
5. Send iMessages through the Message App (your recipient needs to activate iMessage too).
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