Patent ID: 8447815

Claim:
A Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions (SIP/SIMPLE) instant messaging system comprising: a sender mobile communication terminal for generating an instant message delivery report request in the delivery of an instant message; and an SIP/SIMPLE server for: determining if the instant message can currently be transmitted to a recipient mobile communication terminal, if it is determined that the instant message cannot currently be transmitted to the recipient mobile communication terminal, sending a delay message to the sender mobile communication terminal, wherein the delay message comprises an indication that a delivery of the instant message to be transmitted to the recipient mobile communication terminal is being awaited, and waiting without sending an instant message delivery report until the instant message is transmitted to the recipient mobile communication terminal, if it is determined that the instant message can currently be transmitted to the recipient mobile communication terminal, transmitting the instant message to the recipient mobile communication terminal without sending the delay message to the sender mobile communication terminal, and when a response from the recipient mobile communication terminal is received after the instant message is transmitted, generating the instant message delivery report including information on whether or not the instant message is received by the recipient mobile communication terminal and sending the instant message delivery report to the sender mobile communication terminal; wherein the delay message comprises a 202 Accepted response code generated with respect to the instant message.