Deployment Scenarios for Internet Connectivity
Now that you have configured internal mail flow, you are probably interested in learning how you can connect to the Internet so that your users can send and receive Internet mail. This section presents both some common and custom deployment scenarios for Internet connectivity.
Common deployment scenarios describe typical configurations that are used by companies to connect to the Internet, including using Microsoft® Exchange in its default configuration, using a dual-homed server, using an Exchange bridgehead server behind a firewall, and using a Microsoft Windows® relay server.
Custom deployment scenarios include topologies that meet special requirements, such as using a network service provider, configuring cross-forest mail collaboration, and sharing Simple Mail Transfer Protocol (SMTP) mail domains or supporting two SMTP mail domains. Exchange Server 2003 introduces a new tool, Address Rewrite, that can be used to rewrite outgoing e-mail addresses from a subsidiary company. As a result, during a merger or acquisition, all users display the same e-mail address.
Regardless of what scenario applies most to your organization, consider the following tips as you contemplate your own implementation:
If your organization contains multiple servers, you should include gateway bridgehead servers when planning your deployment.
Firewalls offer the most security for Internet connectivity.
SMTP connectors offer a convenient and manageable way to route outgoing Internet mail.
The default SMTP virtual server in its default configuration is sufficient for most scenarios.
If you use multiple SMTP virtual servers on a single Exchange server, be careful when you configure them. By default, multiple virtual servers cannot communicate with one another. For proper mail flow, you need to configure them appropriately so that mail can be routed between them. Additionally, each SMTP virtual server must be configured with a unique Internet Protocol (IP) address and port combination. Generally, all SMTP virtual servers require port 25 so you must assign unique IP addresses to them.
Some companies configure multiple virtual servers on a bridgehead server, with one network interface card (NIC) accepting inbound Internet mail and another NIC routing outbound Internet mail. For more information about this configuration, see Using a Dual-Homed Exchange Server as an Internet Gateway.