smapd - SMTP proxy (server portion) (SMTP =Simple Mail Tranfer Protocol)
The Firewall Toolkit smapd proxy is an application level proxy that provides configurable access control and logging mechanisms. The smap client proxy together with the smapd server proxy, which run on the firewall, transfer mail between internal and external mail servers, using rules you supply.
All packets, and therefore all application requests go to the firewall. On the firewall, the smap and smapd proxy software relay information from one side of the firewall to the other. They prevent versions of sendmail on the exter- nal network from talking with versions of sendmail on the internal network, and vice versa. No IP packets pass from one side of the firewall to the other. All data is passed at the application level.
The server portion of the SMTP proxy (smapd) generally runs as a daemon (invoked from /etc/rc.local). Periodically, based on a configurable value (by default every 60 seconds), the server daemon (smapd) wakes up and checks to see if there is any new mail that the SMTP client proxy (smap) has placed in the spool directory. The smapd daemon checks the headers of the mail for formatting problems. It then calls the configured message transfer agent (usually sendmail in delivery mode) for final delivery.