A device obtains a list of a plurality of user devices from a first network device and receives a message intended for a destination user device from a second network device. The device obtains information indicating that the destination user device can receive messages that conform to a particular format from a third network device and converts the message to the particular format. The device determines a reachability of the destination user device based on the list of the plurality of user devices, after converting the message, and sends the message to the destination user device via the first network device based on the reachability. The device receives a delivery message from the destination user device and sends a notification message indicating successful delivery of the message to the second network device based on the delivery message.