Apple's iMessage service is full of features, fun apps and easy syncing between your Apple devices -- but only if you have it set up properly. It's not uncommon for messages to show up on your iPhone, but not your iPad or Mac or vice versa.

If you're struggling with sending and receiving iMessages on all the things, then follow along.

TL;DR

The gist of what you need to accomplish to ensure all of your iMessage conversations are sent to all of your Apple devices is use the same Apple ID and use just your phone number to send and receive messages. If you need to use an email address as well as your number, double check that the same email address is selected on all of your Apple devices.

It starts with the iPhone

Let's start with making sure everything is set up properly on your iPhone, before we move on to an iPad or Mac.

1. Open Settings > Messages > Send & Receive on your iPhone.
2. At the top of the page is the Apple ID used on your iPhone for iMessage - make note of it. Below will be your phone number along with any email addresses you have associated with your Apple ID.
3. I suggest picking just your phone number as what you will use to send and receive messages. Doing so will prevent a lot of confusion and avoid messages inadvertently syncing to one device.
4. If you opt to select an email address as well, a new option will appear at the bottom of the screen. Select your phone number or an email address as what you want to Start new conversations from.

Now that you have iMessage set up on the iPhone, you need to verify the same information is used on your remaining Apple devices.

On an iPad

1. Open Settings > Messages > Send & Receive and check to make sure the same Apple ID you used on your iPhone is being used on your iPad.
2. If that's the case, then select select your phone number and any email addresses you added on your iPhone.
3. It's very important that you select the same item for the Start new conversations from option at the bottom of the screen as you did on your iPhone.

If the Apple ID doesn't match, you can tap on it and follow the prompts to sign out, then sign in with the same Apple ID you used on your iPhone.

On a Mac

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1. Open Messages then go to Preferences > Accounts and check that the Apple ID used to sign into iMessage is the same as your iPhone and iPad.
2. Check the boxes next to the phone number and email address(es) you want to use.
3. Again, it's very important to select the same item for the Start new conversations from option at the bottom of the screen as you did on your iPhone.

Editors' Note: This post was originally published in 2012, it has since been updated to reflect new features.