SMTP: GW0645: Configuring the SMTP Gateway & DNS (101459)

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  Microsoft(R) Product Support Services Application Note (Text File)
   Configuring the SMTP Gateway and Domain Name Service (DNS): MAIL
                          GATEWAY TO SMTP 3.0
======================================================================
                                                   Revision Date: 7/93
                                                      No Disk included

The following information applies to Microsoft Mail version 3.0.

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INTRODUCTION
============

The Microsoft Mail Gateway to SMTP software depends on another host on
the TCP/IP side of the gateway to route messages from the Microsoft
Mail world to the TCP/IP world. This routing host is referred to in
the "Microsoft Mail Gateway to SMTP" manual as the "smarthost". The
smarthost routes mail both to and from the Microsoft Mail world by
using a group of routing files collectively referred to as the Domain
Name Service. The term Domain Name Service (DNS) is a generic term
common to all implementations of TCP/IP, not just Microsoft's gateway,
and is defined in RFC 1034 and RFC 1035. Thus, you need to configure
two hosts when setting up an SMTP gateway: the host with Microsoft
Mail SMTP gateway software (commonly referred to as the gateway PC)
and the smarthost designated as the DNS. This article concentrates on
how to properly configure the DNS to route Microsoft Mail messages.

CONFIGURING THE DNS
===================

The DNS files include several different routing records. The two types
of records needed to route Microsoft Mail records are the address
record and the mail exchanger record.

Address Record
--------------

The mail address record, also known as an A record in the zone file of
the DNS, defines the IP address to a domain name. For example,
123.123.123.123 might be defined as hostname.dept.company.com.

Mail Exchanger Record
---------------------

The mail exchanger record, also known as an MX record in the zone file
of the DNS, associates a domain name to a domain name defined in an
address record. For example, postoffice.network.company.com might be
associated with hostname.dept.company.com. The exact syntax for
defining mail exchanger records depends on the TCP/IP software the
smarthost is running.


CONFIGURING THE SMTP GATEWAY TO MATCH THE DNS
=============================================

Parts of the SMTP gateway configuration should match exactly what is
defined as an A record and MX record(s) in the DNS. Specifically, when
you select the Administrator program Gateway, SMTP, Setup command, the
Internet Name Of Gateway field must match exactly the domain name
defined in the A record. This is the domain name of the dedicated PC
running the Microsoft Mail SMTP gateway.

NOTE: The smarthost does not have to be the host that has the DNS
running on it. This depends on your site's implementation of the
TCP/IP network and which machine will be responsible for receiving
mail from the gateway.

Also, when you select the Administrator program Gateway, SMTP, Address
Map command, the SMTP Domain field must match exactly the domain name
defined in an MX record in the DNS. The address map must contain all
the Microsoft Mail (gateway and downstream) postoffices that will send
and receive SMTP mail. Each SMTP Domain entry in the address map must
have a corresponding MX record that associates it to the gateway PC's
domain name (Internet Name of Gateway).


EXAMPLE
=======

To make the process clearer, let's follow a message from the SMTP
world to the Microsoft Mail world, using the following assumptions:

 - The domain name of the gateway PC is msmailgwy.company.com, and its
   IP address is 123.123.123.123.

 - The two Microsoft Mail postoffices are named Sales and HQ, and the
   network name is Company. The gateway is attached to the Sales
   postoffice.

 - There is a user named Sparky on postoffice HQ. The DNS resides on a
   host with the IP address of 123.123.1.1.

Configuring the Gateway
-----------------------

1. Set up the DNS with one A record defining msmailgwy.company.com to
   123.123.123.123.

2. Set up an MX record for each postoffice. Set up one MX record to
   define all mail destined for HQ.company.com to be routed to host
   msmailgwy.company.com, and set up another MX record to define all
   mail destined for Sales.company.com to be routed to host
   msmailgwy.company.com.

   NOTE: The MX record for each postoffice including the SMTP HUB should
   map to the UNIX smart host NOT the SMTP gateway. If it maps to the
   SMTP gateway this will allow a foreign SMTP gateway on the Internet to
   connect to and hang the SMTP gateway. If the MX record maps to the
   UNIX smart host the SMTP gateway will only ever talk to the smart
   host.

3. Select the Gateway, SMTP, Setup command to configure the following
   options:

      Domain Suffix:              .company.com
      Internet Name of Gateway:   msmailgwy.company.com
      IP Address of SMTP Router:  123.123.1.1

4. Select the Gateway, SMTP, Postoffices command to configure the
   following options:

      company/HQ
      company/sales

5. Select the Gateway, SMTP, Address Map command to configure the
   following options:

      Enter network name:         company
      Enter postoffice name:      HQ
      SMTP Domain:                HQ.company.com

   -and-

      Enter network name:         company
      Enter postoffice name:      Sales
      SMTP Domain:                Sales.company.com

Sending Mail
------------

1. Mail is sent from the SMTP world to a Microsoft Mail user. The
   sender types in the TO: field something similar to the following:

      Sparky@HQ.company.com

2. The message arrives at the DNS for routing. The DNS looks in its
   files for HQ.company.com. It finds HQ.company.com as an MX record
   and routes the message to host msmailgwy.company.com. The DNS then
   looks in its files for msmailgwy.company.com. It finds
   msmailgwy.company.com as an A record and routes the message to the
   IP address 123.123.123.123.

3. The gateway PC receives the message. It compares HQ.company.com to
   the entries in the address map until it finds a match. It finds a
   match, which tells the gateway PC that HQ.company.com is Company/HQ
   in the Microsoft Mail world.

4. The gateway PC then delivers the message to the HQ postoffice.

   NOTE: The DNS is defined in the gateway PC's TCP/IP software
   configuration and in the Microsoft Mail SMTP gateway software (in
   the Administrator program Gateway, Setup, IP Address Of SMTP Router
   field).
				

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