Under one aspect, a system for transmitting an IP-based message from an initiator to a receiver lacking an IP address via a packet-switched (PS) network capable of communicating IP-based messages and a circuit-switched (CS) network capable of communicating non-IP-based messages, includes: a serving node in communication with the PS network and the CS network, the serving node including logic to: receive the IP-based message from the initiator over the PS network; generate a trigger message responsive to the IP-based message, the trigger message including a non-IP-based message including instructions for the receiver to initiate a connection to the PS network; and transmit the trigger message to the receiver via the CS network, and the receiver including logic to initiate a connection to the PS network and to receive the IP-based message responsive to the trigger message. Methods are also disclosed.