SMS delivery reports are missing on the stock iOS. I’ve come up (and tested) this work around on stock iOS 5.1 on iPhone 4S.
You simply have to add *N# at the beginning of the SMS you would like to have a delivery notification on.
Now i get it that this might be tedious to do on each SMS, so i cane up with this nice tweak to facilitate adding the *N# .
Go to Settings ->;; General ->;; Keyboard , and scroll all the way down to Shortcuts.
And add a new Shortcut for *N# . In my case i chose .,? .
You are set to go. Now whenever you want to get a SMS delivery report just type .,? , or whatever your shortcut is.
Note: the *N# code was tested on the mtctouch carrier. Your feedback for other carriers is highly appreciated