FR

F=R

---

Use a reserved TCP port

V8.6 and above

The F=R delivery agent flag causes sendmail to connect on a reserved (privileged) TCP port for additional security. Privileged Internet ports are those in the range of 0 to 1023. Only root is allowed to bind to such ports. The sendmail program calls rresvport (3) to obtain a socket on its selected port. Note that this is done only when instantiating an outgoing connection.

This delivery agent flag is suitable only for use with the A=TCP delivery agents . Note that sendmail is usually started by root when run as a daemon.