Why is my IMessage sending but not delivering?

I have an iPhone 4 and I'm trying to text a friend and I text them and it says delivered but then a few seconds later it says not delivered. It is doing it to only this one person and it randomly started doing this. When they text me it comes in as text. How can I fix this? What is wrong?

Because you are using an iPhone and iPhones are money down the drain.

  • Why is my iPhone5 sending some messages as iMessage and others as Text Messages? I understand that messages are sent as Text Messages when there's no signal or poor Wi-Fi connection. However, I'm successfully texting some people using iMessage but others (still iPhone users) as Text messages. The other person will send iMessages and then my responses will be sent as green Text Messages.
  • Why does my IPhone keep sending iMessage? My boyfriend had an iPhone but recently down graded to the galaxy s4 xD and every time I send him a text my phone still recognizes it as an iPhone (iMessage) so I have to click on it and send it as a text message every time I send him a text which is so annoying. Does anyone know how to fix this issue?
  • My photos are not sending in group messages, but are sending in individual messages? I'm with Straight Talk Wireless. At first my pictures were sending in the group message but now they are not. I don't know what's wrong, all my settings are what they are suppose to be, and I'm currently on an iPhone 5s IOS 8.4.
  • IPhone not sending iMessage to one person? So I put a friend of mine on do not disturb for a day or two to keep myself from texting them. I took it off and texting was fine. I just realized that a lot of the imessages I've sent him (since Sunday) didn't deliver and they did not automatically switch to text. Why is that happening? I don't believe he would block me he s my best friend. But it is possible.