I'm not sure if SMS supports read reciepts, but I didn't think so. The MMS standard allows for read receipts ("MAY" not "SHALL"), I was unable to get it working, and I suspect it's due to no carrier support.
I was unable to get read receipts working at all, and I suspect it's because the carrier doesn't impliment it.
Delivery receipts, I've edited my comment. I've never been able to get read receipts to work. If I enable it, sometimes I will receive an actual text message that "123-456-7890 has read your message", instead of just marking the message as read.
I'm not sure if SMS supports read reciepts, but I didn't think so. The MMS standard allows for read receipts ("MAY" not "SHALL"), I was unable to get it working, and I suspect it's due to no carrier support.
I was unable to get read receipts working at all, and I suspect it's because the carrier doesn't impliment it.