i have a 8130 pearl. in sms text what is the difference between the checkmark and the checkmark with the D above it? and how come when i am texting people in full service some of the sent messeges have a d over them and some do not? if i resend the test will the person get it more than once?

The "D" means "delivered" to the other device. However, I've noticed that I can send a text and get a "D" and the recipient hasn't actually recieved it so I'm not sure how reliable it is.