3GPP 23.501 v20.2.0 — the document's own text
4.4.7 MSISDN-less MO SMS Service
Taught in 21. Emergency calls, messages, voice and location (The 5G system architecture, in depth).
MSISDN-less MO SMS via T4 is subscription based. The subscription provides the information whether a UE is allowed to originate MSISDN-less MO SMS.
The UE is pre-configured with the Service Centre address that points to SMS-SC that performs this MO SMS delivery via NEF delivery procedure. The recipient of this short message is set to the pre-configured address of the AF (i.e. Address of the destination SME). If UE has multiple GPSIs associated to the same IMSI, the GPSI that is associated with an SMS may be determined from the UE's IMSI and the Application Port ID value in the TP-User-Data field (see TS 23.040 [5]). The NEF may obtain the GPSI by querying the UDM with the IMSI and application port ID.
UE is aware whether the MO SMS delivery status (success or fail) based on the SMS delivery report from SMS-SC. The network does not perform any storing and forwarding functionality for MO SMS.
See clause 5.2.6 of TS 23.502 [3] for a description of NEF Services and Service Operations.