iMessage is one of my favorite new features in iOS 5. It’s simple, fast, and most importantly integrated right into the Messages app, which makes it even more compelling, assuming you have friends with iDevices as well.

If you have an iPhone your iMessages are sent to your phone number by default, which acts like your iMessage ID, if you will. If you have an iPad, you can only receive iMessages sent to your registered email address. But what happens if you want to receive all your iMessages on all of your iDevices?

Fortunately, Apple thought that through, and they you can add an email address as your iMessage ID on your iPhone as well.

Making an Email Address Your iMessage ID

Navigate to Settings > Messages > Receive At > Use Your Apple ID for iMessage on your iPhone.

If you do not want to use your Apple ID for iMessage, you can always choose “Add An Email” from the same Settings page, and add whatever email address you want people to send iMessages to, but make sure it is the same as the one used on your iPad or iPod touch.

By doing this, you will be able to receive iMessages sent to your phone number, but also messages sent to your email address. Obviously, you will have to let people know they can iMessage you at this address.

From now on, anytime someone sends you an iMessage to your email address, both your iPhone and iPad will receive it.

Sending iMessages From the Same ID

You can’t control where you receive your iMessages (either email or phone number), but you sure can control where you send them from.

If your goal is to centralize all iMessages, you also want to set the same caller ID on all your devices. Like the name suggests, the caller ID is the email or phone number used to send the iMessage. Basically, you can tell your iPhone to either send messages from your phone number, or from your email address.

Because we’re trying to turn all our devices into central hubs, we want to use an email address as caller ID, and make sure that this same email address is set as the caller ID on all of your iDevices.

To set this up (once you have added at least one email address), go back to Settings > Messages > Receive At > Caller ID, and select your email address.

Repeat this for all your iDevices.

Going Forward

From now on, all your iMessages will be sent with your email address as the caller ID. This means that even if someone doesn’t know your email address as your ID, they will still receive messages from you showing the email address as the ID, and iMessage will take care of the rest, making sure that if this person replies, it will be sent to your email ID on all your devices.

Now what happens if someone doesn’t know your email address and sends you an iMessage to your phone number? Well, you will only get that iMessage on your phone, and there is nothing you can do about that.

When that happens to me, the first thing I do is delete the iMessage conversation with this person, then I start a new one, which is going to be initiated with my email address as the caller ID. When this person hits “reply” to reply to your message, it will be sent automatically to your email address because it’s the one you sent the message from in the first place. Confusing? Yeah, I know.

Alternatively, you can always tell people to add your email address to their contacts and use this going forward.

I realize all this can be a bit confusing but, unfortunately, this is the best way to go about it. Hopefully Apple will figure out a way to let iPad owners who also own an iPhone use their phone number for iMessages on the iPad as well, but this is just not possible at the time.

I hope this tutorial helps. Let us know if you have questions or comments.