couriertls(1) on Linux
The text 960ac52fd8e5, as Debian 12 (Bookworm), Debian 11 (Bullseye) shipped it.
the Courier mail server TLS/SSL protocol wrapper
Flags it lists
-
-host -
-localfd -
-port -
-printx509 -
-protocol -
-remotefd -
-server -
-statusfd -
-tcpd -
-user -
-verify