help with SMS on iPhone

hi...im still relatively new to the iphone...ive had it for about 2 weeks...so ive figured out most of the stuff...but this one very basic thing i cannot seem to figure out...

how do you know if the message you just sent was delivered or not?
im using an iphone 4 running 4.1

There is a progress bar at the top that says "sending". When it is sent, the bar goes away. That's how you know.

If the message has not sent you will have a (!) next to the particular message as well as the sms icon on your home screen.

- Mike

yea...it was easy for me to figure out the progress bar that shows while sending...my concern is about the actual delivery of the sent message...sometimes a message that may have been sent does not get delivered to the recipient...on all phones i ave used previously there is an optional alert you can toggle which tells your if the delivery was successful or not...
im trying to figure out how to see that on the iphone