A smart host is a mail server is used to deliver your mail and is also called a mail relay. This eliminated the need for DNS MX record resolution so you save the time it takes to do external resolutions. That said, DNS traffic is usually very fast and hardly consumes any bandwidth. It is more likely that your mail will actually be delivered slower if you use an ISP smart host, which usually is very busy and has a large queue.

The upside of using an ISP smart host is you send a single e-mail with a large attachment to say twenty recipients that mail will only be sent once through your wires. The smart host will create twenty separate e-mails to be sent to their destinations.
This is especially useful for companies using ADSL, which has a limited upload ratio. However, not all ISPs are generous enough to let you route all your mail through their servers.

To set up a smart host go to Exchange System Manager and open the property page of your SMTP Connector.

The information in this article applies to:

• Microsoft Exchange 2000 Server