Our delivery rate is on average 98% delivered SMS and MMS.  We have one of the highest delivery rates in the industry.  Our intelligent messaging technology detects automatically if the mobile network is not available, and tries to resend the message until we receive confirmation from the carrier that the SMS or MMS is accepted. If the message is not delivered, there are several possible reasons:    - Number is globally opted out or blocked (by carrier or recipients).    - Recipient has blocked incoming messages from Short Codes or in general.    - Bad reception and mobile carrier cannot receive acknowledgement that the message is received by the handset.    - Content of the message is blocked due to the valuation of MMA and CTIA best practices and guidelines. Sometimes, message is delivered but delivery reports are not updated quickly.  Our system monitors all messages with "pending" status and re-checks delivery status until we receive the final and most accurate message delivery status. Some messages may return an unknown error code. Number Blocked by Carrier. The recipient should ask their carrier to enable SMS on their plan Others, with Rejected status, we have checked with the carriers and received a very generic error from our carrier partner that we have no further details about. They did not provide any reason why it was not delivered. There might be several factors: mobile number has been blocked or not able to receive SMS, or we simply have not received the proper delivery report.