I just got a new iPad, and I have my iPhone set to my email address as my caller ID. I'm using the same email address (my Apple ID) for iMessage on both devices. However, when I send an iMessage from one device, it says "not delivered" on that device, and instead successfully delivers it through the other device. Sometimes it does not successfully deliver it at all. Shouldn't it sync as successfully delivered on both devices? Is this how it's supposed to work?