iOS 6 SMS message delivery reports
SMS delivery reports are a network feature, not a phone feature, so theoretically you might need to contact your carrier, to get more information and to check with them. Separately from it, confirmation has to be enabled/sent by recipient, I remember my old phone had this setting set to off.

iMessages, have separate notifications and format, as they are not real SMS, but are working between iPhones, iPads, iPods and Macs. If Wi-Fi is unavailable, iMessages will be sent over cellular data. Carrier cellular data fees might apply.

Activate/Enable iPhone SMS and iMessage Delivery Report


Tap Settings on the Home screen and select Messages.
Tap the Off button within the iMessage section of the Messages screen so that the button reads On.
Tap the Off button in the Send Read Receipts section so that it reads On.
Tap Settings to return to the Settings screen and to save your preferences.