To find out if a message has been delivered in Apple Messages, open the Messages app → select a conversation and → check that it appears under your last message.
Method 1 Under iOS
1 Tap the Messages app.
2 Tap a conversation.
3 Tap the text field just above your keyboard.
4 Enter a message.
5 Press the button containing a blue arrow. Your message is then sent.
6 Look for the indication Distributed under your last message. This will be displayed below the text bubble of the last message you sent.
If you don't see marked Distributed, look at the top of your screen if Sending in progress... or Sending in progress from 1 on
If nothing appears below your last sent message, your message has not yet been transmitted.
If the Read Confirmation has been activated by your recipient, then Read will be displayed once he (or she) has actually read your message.
If you see Sent as SMS, it means that your message was sent through your carrier's SMS service and not through Apple's iMessage servers.
Method 2 On Mac
1 Open the Messages app.
2 Click on a conversation.
3 Enter a message.
4 Press Enter.
5 Look for the indication Distributed under your last message. This will be displayed below the text bubble of the last message you sent.
If the Read Confirmation has been activated by your recipient, then Read will be displayed once he (or she) has actually read your message.
If you see Sent as SMS, it means that your message was sent through your carrier's SMS service and not through Apple's iMessage servers.
If you don't see anything appear below the last message you sent, it may not have been delivered yet.
Advice
Your message may not have been delivered for several reasons. Your device may not be properly connected to the network or Wi-Fi, your recipient's device may be turned off or out of Wi-Fi range, or your recipient may have blocked you.