A communication system, comprising: a plurality of messaging systems (351, 352) for delivering messages based on a respective message signaling protocol (341, 342); a plurality of packet core networks (311, 321, 312, 322, 313, 323, 314, 324, 315, 325), wherein each packet core network is designed according to a respective packet core network technology; a subscription and location server, configured to store for each subscriber of a plurality of subscribers associated with a corresponding User Equipment, UE: a subscriber identity; a subscriber location indicating in which packet core network of the plurality of packet core networks the subscriber is located; and an indication that a Universal Packet Signaling Messaging System, UPSMS, service is supported; and a UPSMS system, configured to extend a message received from one of the messaging systems (351, 352) based on a message signaling protocol extension that extends the message signaling protocol (341, 342) by including an indication that the UPSMS service is supported for a respective subscriber, and to forward the extended message to the subscription and location server, wherein the subscription and location server is configured to authenticate a subscriber based on the subscriber identity, and to identify for an authenticated subscriber, for whom the UPSMS service is supported, a packet core network of the plurality of packet core networks that is connected to the corresponding UE, based on the subscriber identity, and to deliver the extended message via the identified packet core network to the corresponding UE. a plurality of messaging systems (351, 352) for delivering messages based on a respective message signaling protocol (341, 342); a plurality of packet core networks (311, 321, 312, 322, 313, 323, 314, 324, 315, 325), wherein each packet core network is designed according to a respective packet core network technology; a subscription and location server, configured to store for each subscriber of a plurality of subscribers associated with a corresponding User Equipment, UE: a subscriber identity; a subscriber location indicating in which packet core network of the plurality of packet core networks the subscriber is located; and an indication that a Universal Packet Signaling Messaging System, UPSMS, service is supported; and a subscriber identity; a subscriber location indicating in which packet core network of the plurality of packet core networks the subscriber is located; and an indication that a Universal Packet Signaling Messaging System, UPSMS, service is supported; and a UPSMS system, configured to extend a message received from one of the messaging systems (351, 352) based on a message signaling protocol extension that extends the message signaling protocol (341, 342) by including an indication that the UPSMS service is supported for a respective subscriber, and to forward the extended message to the subscription and location server, wherein the subscription and location server is configured to authenticate a subscriber based on the subscriber identity, and to identify for an authenticated subscriber, for whom the UPSMS service is supported, a packet core network of the plurality of packet core networks that is connected to the corresponding UE, based on the subscriber identity, and to deliver the extended message via the identified packet core network to the corresponding UE.