What does it mean when an iMessage doesn't say "Delivered" nor "Not Delivered"?

I sent an iMessage to a friend, and at the bottom it doesn't say "Delivered" as it usually does. It doesn't say "Not Delivered" either, it just doesn't say anything at all.

What does it mean when an iMessage doesn't say "Delivered" nor "Not Delivered"?

Solution 1:

The receiving device is probably off, in sleep mode, out of cell reception, flat battery - something like that.

Solution 2:

I believe "Not Delivered" implies an error of some kind, whereas if nothing is displayed that just means the message is queued up to an inactive phone, or backed-up in transit over the network.

Solution 3:

It can mean a few things;

• The recipients' phone battery is low/dead
• The recipients' phone is out of wifi range.
• The recipient has you on block
• The recipients' phone is off