Abstract: A method comprises registering, by an enhanced CPM server, to receive IMS registrations for a client device, receiving, by the enhanced CPM server, a message intended for the client device, storing the message in a network store, setting a Message Waiting Indicator flag in a HLR associated with the client device, receiving, from the HLR, an alert message that the client device has registered in a non-IMS network, and delivering, by the enhanced CPM server, at least a reference to the message stored in the network store to the client device.

Abstract: An IP Multimedia Subsystem (IMS) Centralized Services (ICS) Interworking Function (IWF) element comprises an i2 interface to an IMS core network, an i3 interface to a Telephony Application Server (TAS), a Mobile Applications Part-G (MAP-G) interface to a Mobile Switching Center (MSC) for retrieving subscriber identity, a MAP interface to a Home Location Register (HLR) for location management, subscriber management and call handling procedures, and an Sv interface to a Mobility Management Entity (MME) for appearing as a Visitor Location Register (VLR).

Abstract: A method comprises registering, by an enhanced CPM server, to receive IMS registrations for a client device, receiving, by the enhanced CPM server, a message intended for the client device, storing the message in a network store, setting a Message Waiting Indicator flag in a HLR associated with the client device, receiving, from the HLR, an alert message that the client device has registered in a non-IMS network, and delivering, by the enhanced CPM server, at least a reference to the message stored in the network store to the client device.