SMTP: SMTP Gateway in Small, Medium, and Large Organizations

The information in this article applies to:

• Microsoft Mail Gateway to SMTP, version 3.0

SUMMARY

You can deploy the Microsoft Mail Gateway to SMTP in several physical ways within an organization. The model you choose depends on both the volume of mail moved to and from SMTP and the external-postoffice routes defined within your Microsoft Mail for PC Networks postoffice(s).

This may be an issue for your organization because the Gateway to SMTP will only move one message in or out of Microsoft Mail at a time. As a result, it may become a bottleneck for the SMTP mail flow.

For additional information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q87045
   TITLE     : SMTP: What the Gateway to SMTP Does

MORE INFORMATION

Single Gateway Solution (Small Organization)

Typically, the Gateway to SMTP is installed on one Microsoft Mail postoffice (a gateway postoffice) and other postoffices (downstream postoffices) will send or receive SMTP mail via the single gateway postoffice . This solution works well for most organizations. However, when the volume of an organization exceeds the physical limitations of the SMTP gateway: roughly 10,000 messages per day (average message size approximately 8 kilobytes) a bottleneck can occur.

    _______                    _______                   _______
   |Downstm|                 | Gateway |      SMTP      | Smart |
   |  PO   | -<--External-->-|  PO     |-<---Gateway-->-| Host  |
    -------                   ---------                  -------

Multiple Gateway Solution (Small/Medium/Large)

One way to workaround the bottleneck described above is to purchase several copies of the Microsoft Mail Gateway to SMTP and install them on postoffices within the Microsoft Mail environment. The Microsoft Mail downstream postoffices may then be logically divided into groups so that they evenly distribute the traffic of SMTP mail between the multiple gateways.

This model is useful for organizations that need to move large volumes of SMTP mail, and for organizations that have complex external-postoffice routes defined.

    _______                   _______                   _______
   |Downstm|                 |Gateway|     SMTP        | Smart |
   |  PO   | --<->-|---<->---|  PO   |-----Gateway-<->-|  Host |
    -------        |          -------                   -------
                   |                                     ^
    _______        |                                     |
   |Downstm|       |                                     |
   |  PO   |--<->--|                                     |
    -------        |                                     |
    _______    External       _______                    |
   |Downstm|       |         |Gateway|     SMTP          |
   |  PO   | -<->--|---<->---|  PO   |-----Gateway--<->---|
    -------        |          -------
                   |
    _______        |
   |Downstm|       |
   |  PO   | -<->--|
    -------

Dedicated Send/Receive Gateways (Medium/Large Organization)

Another way to workaround the bottleneck issue is to divide the responsibilities of a single SMTP gateway on to two IBM-compatible computers. One computer is dedicated for moving mail from Mail to SMTP (send); the other can be responsible for moving mail from SMTP to Microsoft Mail (receive).

Once configured these gateways become independent gateways, each limited only to its own capacity (refer to article on Theoretical Performance of the SMTP Gateway). However, this configuration should only be used when each dedicated gateway has a dedicated gateway postoffice.

The following is a logical drawing of message routing:

    _______
   |Downstm|
   |  PO   |                    _______      Sending     _______
    ------- --<->---|          |Gateway|     SMTP       | Smart |
                    |-->---->--|  PO   |-->--Gateway->--|  Host |
                    |           -------                  -------
    _______         |                                         |
   |Downstm|--<->---|                                         |
   |  PO   |        |                                         |
    -------      External                                     |
    _______         |                 _______     Receiving   |
   |Downstm|--<->---|                |Gateway|    SMTP        |
   |  PO   |        |-----<-----<----|  PO   |-<--Gateway--<--|
    -------         |                 -------
                    |
    _______         |
   |Downstm|--<->---|
   |  PO   |
    -------

Configuration Summary

First configure a single IBM-compatible computer to successfully move SMTP mail bi-directionally (as if will be the only computer responsible for SMTP traffic). Once this gateway computer is a functional SMTP gateway, then set up a second computer with the exact same configuration and batch files, except using a different TCP/IP number.

Notes:

• Do not try to load the gateway on both computer simultaneously.
• You do not need to add an Address Record on your Smart Host for the second computer.

   ARTICLE-ID: Q101459
   TITLE     : SMTP: GW0645: Configuring the SMTP Gateway & DNS

1. Copy SMTPGATE.EXE and SMTPPUT.EXE to the local hard drive of this computer. This is required.

   IMPORTANT: Do not copy SMPTGET.EXE to the local drive.

2. Modify your configuration files to locate the local executable files, and remove the server executable location from the path statement.

3. Modify the gateway command line options to configure it for INBOUND SMTP mail.

   NOTE: When this inbound gateway (SMTPGATE.EXE) cycles through its routine, it will try and locate SMTPGET.EXE. It will take approximately three (3) seconds to fail before it proceeds back to its designated receive mode. This error will be displayed on screen.

4. Your first computer is now ready to act as a dedicated "Inbound SMTP Gateway."

         Example Inbound SMTP Command Line:
   

         SMTPGATE  -w32767 -i63 -md -lascy -ci -gascy
   

1. Copy SMTPGATE.EXE and SMTPGET.EXE to the local hard drive of this computer. This is required.

2. Modify your configuration files to locate the local executable files, and remove the server executable location from the path statement.

   IMPORTANT: Do not copy SMTPPUT.EXE to the local drive.

3. Modify the gateway command line options to configure it for OUTBOUND SMTP mail.

   NOTE: When this outbound gateway cycles through its routine, it will try and locate SMTPPUT.EXE. It will take approximately three (3) seconds to fail before it proceeds back to its designated receive mode. This error will be displayed on screen.

4. Your second computer is now ready to act as a dedicated "Outbound SMTP Gateway."

         Example Outbound SMTP Command Line:
   

         SMTPGATE  -w120 -q180 -063 -md -ln -ci -gascy -ms
   

   NOTE: Because the SMTP Gateway is designed to write all temporary files in M:\SMTP\*.*, each dedicated gateway (send or receive) will be using the same temporary directory. If a single postoffice is used to support both dedicated gateways, it will only be a matter of time until the two gateways begin to process each others temporary files (that is, message parts).

   Ultimately, the gateways will lock on a temporary file and halt mail in both directions, requiring human intervention: a reboot of both gateways.

Multiple Dedicated Send/Receive Gateways (Medium/Large Organizations)

The above can be adapted for an even more intense SMTP Gateway configuration.

         _______
        |Downstm|
   |-<>-|  PO   |--------|           _______      Sending     _______
   |     -------         |          |Gateway|     SMTP       | Smart |
   |                     |-->---->--|  PO   |-->--Gateway->--|  Host |
   |                     |           -------                  -------
   |      _______        |                                         |
   |    |Downstm|--------|                                         |
   |-<>-|  PO   |        |                                         |
   |     -------      External                                     |
   |     _______         |                 _______     Receiving   |
   |    |Downstm|------- |                |Gateway|    SMTP        |
   |-<>-|  PO   |        |-----<-----<----|  PO   |-<--Gateway--<--|
   |     ------          |                 -------
   |                     |
   |     _______         |
   |    |Downstm|--------|
   |-<>-|  PO   |
   |     -------
 External
   |     _______
   |    |Downstm|
   |-<>-|  PO   |                    _______      Sending     _______
   |     ------- --------|          |Gateway|     SMTP       | Smart |
   |                     |-->---->--|  PO   |-->--Gateway->--|  Host |
   |                     |           -------                  -------
   |     _______         |                                         |
   |    |Downstm|--------|                                         |
   |-<>-|  PO   |        |                                         |
   |     -------      External                                     |
   |     _______         |                 _______     Receiving   |
   |    |Downstm|------- |                |Gateway|    SMTP        |
   |-<>-|  PO   |        |-----<-----<----|  PO   |-<--Gateway--<--|
   |     -------         |                 -------
   |                     |
   |     _______         |
   |    |Downstm|--------|
   |-<>-|  PO   |
         -------