In Exchange Server 5.5, I had to use the Internet Mail Service (IMS) to exchange mail with Internet hosts. In Exchange 2000 Server, if I don't change any default configuration settings, SMTP works fine. Why would I want to set up an SMTP connector?

Exchange 2000 uses SMTP as its core transport protocol. Assuming that you've set up TCP/IP and DNS properly and that you supply the right domain name to Exchange 2000, Exchange 2000 will happily send and receive SMTP mail without any special effort on your part because it installs the SMTP virtual server component by default. So why would you bother with an SMTP connector when the default configuration seems to work so well? The SMTP connector lets you set up separate connectors for separate address spaces and designate individual servers in a routing group as bridgeheads. This configuration is similar to what many large sites did with the Exchange 5.5 IMS. Setting up an SMTP bridgehead at the edge of your network lets you concentrate traffic into one server for archiving, content or virus scanning, and flow control.

The SMTP connector also provides other functionality missing from the default virtual server. This additional functionality includes

  • choosing whether you want SMTP mail to flow all the time or on a particular schedule. You can even define a separate connection schedule for messages that exceed a specified size.
  • using the SMTP connector to automatically dequeue mail held at a remote site. This capability is a natural way to periodically schedule connections to a smart host and pick up your mail, all in one go.
  • setting delivery restrictions that allow—or disallow—mail from particular senders. You can also restrict the passage of messages according to their priority, origin (i.e., system or nonsystem), and size.
  • limiting a connector to a particular address space, which lets you set separate schedules and behavior for different destination domains.
  • specifying whether you want a connector to forward all mail to a smart host. Forwarding mail to a smart host lets you focus all your mail on one machine, at the cost of taking away your flexibility in setting routing options. Of course, if you want to build a routing architecture that tightly channels message flow, this method is the way to do it.