Hi,
Getting back Read Receipts are dependant on how you addressed the outgoing iMessage.
So, lets presume you sent it to an iPhone Number.
That means you addressed the iPhone of that person.
If their iPhone is set up to respond with Read Reciepts then you will see it only if the person reads it on the iPhone.
This is true even if their Mac is set up to Dispaly messages sent to the iPhone Number on the Mac na d if it is set to respond to send Read Receipts (as these are likely to be for the Apple ID).
This means that if you indeed Addressed an Apple ID (And therefore a Mac most likely) then you will not get a Read Receipt until the iMessages was read on that device.
This can mean that you get some Receipts much later if the person reads the iMessages on a device much later.
This can happen where a person might only have an iPhone and an iPad where the iPad will be set up to use and Apple ID rather than a phone Number.
AS to the Green (SMS/Text) messages that your iPad shows I am not sure.
An iPhone is normally the device that can send SMS and these can be setr up to be forwarded to the MAc and any other device using the Apple ID over the same LAN.
However if your iPad is one that can use a SIM Card then it may be acting like an iPhone and it could be the device sending SMS and Forwarding them to your Mac.
Once this has been set up you can send SMS from your Mac via the shared link to the phone service carrier.
Having said that my SMS conversations don't show Read Receipts so I am not entirely sure what is going on here.
