worth mentioning that SMS messages are plaintext as they traverse the carrier network. They are also logged by seemingly any equipment that they traverse. Also when they aren't delivered immediately, they wait in a queue on the network waiting for the receiving device to "phone home" (pun intended 😎).

The caveat here is often times the plaintext message is in an encrypted tunnel (physical wireless layer, and data tunnels in carrier EPC) but at tunnel endpoints, SMSs are nakey