One of the many problems we've seen on iPhones and iPads since the official launch of Apple's iOS 7 is iMessages not being consistently delivered for some users. Very often, users won't even notice that a message hasn't been sent; not until the intended recipient says "I never got your text."
Here's how to tell whether an iMessage has been sent (it's not easy), and how to force it through if it hasn't.
Go to the Messages app in your iPhone. Open any thread. At the very top of the screen, check whether it says "Sending…" or "Sending 1 of X" (as seen in the image below).
That's your primary indication that a message was never delivered.
Any of your messages that say "Delivered" beneath them are in the clear. But iMessage doesn't label all delivered messages in that way (which is horribly inconsistent and confusing). Some messages will have a time and date stamp above them, but you can't always tell whether this applies to a string of messages or just the one directly beneath it. If you see a blue iMessage with no "Delivered" label (again, see the label in the image below), it's probably one that has not been sent.
Press and hold any suspect blue message, and an option for "Send as Text Message" will appear.
That button will force the message to be delivered outside iMessage, and sent through your mobile phone network instead. The message will turn green to indicate it was sent via text instead of iMessage, and you'll see a notification below it saying "Sent as Text Message."
Now let's say you would rather delete the message than send it now. If you press and hold any blue undelivered message and select "More," the app lets you select several messages to delete at once.
Mark any suspect unsent messages to delete and hit the trash bin icon. If the "Sending…" message at the top of the app disappears, you'll know you've nixed all the faulty messages — from that thread only, though.
This solution is clunky and imperfect, but it's good to know you have some recourse for taking control of your messages when iMessage fails.
For more on iOS 7, check out our 6 handy tips, and our guide to improving the iPhone 4S and iPhone 5's battery life under iOS 7.