My girlfriend uses the iPad 2 during the day and I have my iPhone 4. I use the same apple id on both devices, but have different email addresses. When I try to send a message from the iPad to the iPhone I get an error. Do I need to different apple ids for each device? Also, when I go to General > Setting > Messages and try to change the email from mine to hers I get an error from iMessage Activation saying Unable to verify email because it is already in use.