A problem that's been going on for a while, my friend has no problem sending me text messages from his iPhone, but when I try to message him back, I never get the "delivered" confirmation, and I find out later that he never got the message.

I've been trying to message him for a couple of days with no success, and finally I tried phoning him. It rang once, and was just starting to ring a second time when the line went dead.

I have no problem texting other people with or without iPhones. It's just this one person that there's a problem with. Any ideas what might be wrong?

Has your friend checked with some other people to see if this problem is on your end...or his?

I don't think he's checked with anyone else. Unfortunately, he's so technically incompetent that it's impossible to discuss these things with him. So, I'm trying to get some ideas before I discuss it with him. If I don't have a quick and easy solution for him, he won't be interested in fixing the problem.

I'm assuming (maybe incorrectly) that since I haven't had any problems texting anyone else, I don't think the problem is on my end.

It almost seems as if he powers his phone off whenever he's not using it. But even so, when he powers it on again, any pending unreceived message should then come in to his phone shouldn't they?

I was wondering if iOS has some kind of "ignore" option to block messages and calls from particular people, that he may have inadvertently activated. I've never seen anything like that, but then I'm not an iOS power user by any means.

If the message is undeliverable, you should get a red exclamation mark. If a message can’t be delivered as iMessage, it will be delivered as regular text message (unless you disabled that), and you should see the green bubble instead of the blue bubble.

What if you have his phone number listed differently from what he has listed with his Apple ID, or vise versa? That could create a weird mix up.

Assuming your friend is in your Contacts list with full details;
Start a new message, instead of replying. Start filling in the ‘To:’-field. A list with matching options should show, color coded: blue is contacts with Apple ID, green is SMS/MMS text-message only, gray color is unknown/not used before for messaging (e.g. land lines). Contacts with multiple means of contact, will have multiple listings. Pick a blue listing. Apple should deliver that to the matching Apple ID as iMessage, and that is all you can do on your end.

If you can walk your friend through getting there in Settings > Messages > Blocked there is a list of the phone numbers, addresses, etc that have been blocked on that phone. The list is editable.

Well, apparently I haven't been blocked. After about a week, all of the messages that I sent are now showing that they've been delivered. My suspicion is that he simply had his phone turned off.