The operation of the mailer is quite simple. An alias is placed in the PMDF alias file that forwards messages sent to a special mailbox name (usually MAILER) to the BITNET gateway channel. BN_GATEWAY then runs as the channel master program. It discards the PMDF envelope and the initial RFC 822 header on the message. The message body is passed to the SMTP command interpreter for execution. The message is deleted after it has been executed.