Mail Routing Host
The Microsoft Mail Gateway to SMTP depends on a mail routing host in the
TCP/IP network to route its mail. This is the host defined in the
Administrator program under Gateway, SMTP, Setup, in the IP Address of SMTP
Router field. The mail routing host is sometimes referred to as the smart
host.
The mail routing host routes mail in two ways:
- Domain name service (DNS)
- Hosts file, usually kept in \ETC\HOSTS
For details on the DNS, see the application note "Configuring the SMTP
Gateway and DNS" (GW0645).
Hosts File Contents
The hosts file is a flat file on the mail routing host that consists of
two vital pieces of information: IP addresses and host domain names.
The gateway computer must have an entry in the host file, and so must the
domain names assigned to Microsoft Mail postoffices. Domain names are
assigned in the Administrator program, under Gateway, SMTP, Address Map,
in the SMTP domain field.
For example, the entries in the hosts file for the gateway computer
MSMAILGWY.COMPANY.COM at IP address 123.123.4.5 that has Mail postoffice
domain names of HQ.COMPANY.COM and SALES.COMPANY.COM, would look like this:
123.123.4.5 MSMAILGWY.COMPANY.COM
123.123.4.5 HQ.COMPANY.COM
123.123.4.5 SALES.COMPANY.COM
This ensures that mail addressed to SPARKY@HQ.COMPANY.COM is routed to
the gateway computer by the SMTP host for processing by Mail.