Using MS Exchange or Other SMTP Mail Servers w/ Proxy Server 2.0

The information in this article applies to:

• Microsoft Proxy Server version 2.0

SUMMARY

There are two methods of using Microsoft Exchange Server (or other Winsock-based server applications) with Proxy Server version 2.0.

• Co-locate the Microsoft Exchange services on the Proxy Server 2.0 server.
• Install Microsoft Exchange Server on a separate computer located on the internal network behind the Proxy Server 2.0 server. Use the Server Proxy feature of Proxy 2.0 to redirect the listen() call of the Microsoft Exchange services.

MORE INFORMATION

Co-locating Microsoft Exchange with Proxy 2.0

If the Microsoft Exchange services are installed on the Proxy Server, it will be able to listen for connections from any network interface. For example, mail clients or SMTP servers on the Internet or intranet will be able to send and receive mail with the Microsoft Exchange Server.

If Proxy Server 2.0 packet-filtering feature has been selected (enabled), all connections from mail clients or servers on the Internet will be blocked. In fact, all communications except for ICMP requests to and from the Proxy Server will be blocked. However, applications that use any of the Proxy services will still be able to communicate with the Internet with the use of the Proxy Server dynamic packet-filtering feature.

Because the Microsoft Exchange Server is installed on the Proxy Server computer, it will not be using the Proxy services to communicate with the Internet. The communications will be blocked unless a static filter is enabled on the Proxy packet filter interface for each of the Microsoft Exchange Server services.

To create a new packet filter using predefined filter definitions:

1. In the Security dialog box on the Packet Filters tab, click Add.

2. In the Packet Filter Properties dialog box, under Allow this Microsoft Windows NT Server to Exchange Packets of Type, click Predefined filter and select a protocol (in this case, select SMTP).

3. By default, the predefined filters will allow communication to/from ANY host on the Internet. If needed, modify the Local Host and Remote Host settings before you click OK.

4. Click OK.

5. Repeat steps 1-4 to add the POP and IDENTD filters.

MORE INFORMATION

Server Proxy feature allows you to place a server application (such as FTP, SMTP, POP, or Telnet) on the private network behind the Proxy Server. With this configuration, the packet filtering features of Microsoft Proxy Server 2.0 can protect a mail server or other server application. The application will not require additional valid Internet IP addresses.

For each Windows Sockets-based application to work through a network connection, the ports are used in combination with IP addressing to form a "socketed" connection. The WinSock Proxy service can also redirect a listen() call, which means that Proxy Server can listen to Internet requests on behalf of your internal Microsoft Exchange mail server or other server application and redirect them appropriately.

For example, if you have bound an internal SMTP/POP server to the proxy, mail clients, or SMTP servers on the Internet, you can contact this server by connecting to the Proxy Server's Internet address. To the outside world, these services will appear to be running on the Proxy Server itself.

WARNING: The Server Proxy feature allows an application behind the proxy to accept connnections from Internet hosts. If the DATA portion of a packet has been maliciously modified, the application using the server proxy feature may be vulnerable to attack by a client sending invalid commands or bad data to the application.

The Server Proxy feature is covered in detail in the product documentation for Microsoft Proxy Server version 2.0. Please see the "Configuring Server Proxy Parameters" section in the "Configuring Multiserver Environments" chapter.

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

ARTICLE-ID: Q181420

TITLE     : How to Configure Exchange or Other SMTP with Proxy Server