Disclosed is a network-based device in an IP Multimedia Subsystem (IMS) that provides IMS services to terminating non-IP devices. The method embodiment includes receiving a REGISTER message that initiates registration of a Public User Identity (PUID) at a terminating non-IP device at a network-based device in an IMS, wherein the terminating non-IP device is specified as being at an E.164 routing address, establishing, in a network device that accepts communications regarding where to send sessions destined for a specific PUID and provide information regarding where to send sessions, the E.164 routing address as a final destination of sessions to the PUID based on the registration and an IP address of a network device that includes routing functionality based on telephone numbers as an immediate destination for the session and using this information from the registration to route to the terminating non-IP device after providing IMS services by using the relationship between the PUID, the E.164 routing address and the IP address of the network device that includes routing functionality based on telephone numbers that completes the routing of messages to the terminating non-IP device that was established during registration.