Is there a way to know if an SMS message is actually delivered to my recipient?
Yes. For both GSM and SMPP it’s possible to request a delivery report to be sent back to you when an SMS message reaches a final state. For GSM modem this is sometimes called a ‘Status Report’.
After sending the SMS message check the Reference property of the message you just sent to get a reference that was returned by the provider. This reference will be used to reference this message in the delivery report as well.
On an SMPP connection a delivery report is just an ordinary SMS message with the property SmppIsDeliveryReport enabled. On SMPP you can either parse the message to find the reference and ultimate message status or check for optional TLV values. Some providers use SMPP_TLV_RECEIPTED_MESSAGE_ID tag and the SMPP_TLV_MESSAGE_STATE TLV’s to convey this information as well.
Download the trial version of the Auron Component to find some examples on how to receive delivery reports.