A tip that has been useful to my clients is to use the built-in SMTP server in Microsoft IIS. (This component is included in Windows 2000 and the Microsoft Windows NT 4.0 Option Pack.) The SMTP component is useful for laptop users who switch between accessing their POP accounts through a dial-up connection and a high-speed connection from home. To install your own SMTP server, go to Win2K's Control Panel Add/ Remove Programs applet, select Add/Remove Windows Components, scroll down to and select the Internet Information Services (IIS) check box, and click Details. In the resulting dialog box, select the SMTP Service check box, which causes Win2K to install IIS as well as Web server components. After you complete this process, you can ensure that the service is working properly by entering the following command at a command prompt:
telnet 127.0.0.1 25
If the service is working, the Telnet session comes up with an Enhanced Simple Mail Transfer Protocol (ESMTP) mail service message.
After you confirm that the service is working, configure the SMTP service that comes with Win2K: Click Start, Administrative Tools, Internet Information Services, and use the tabs of the resulting dialog box to set up IIS. The most important settings are on the Access tab, on which you can specify the computers or block of IP addresses that can relay SMTP mail through your server. I set up my clients' systems to accept only connections from the localhost (127.0.0.1). This configuration prevents other systems from connecting to my SMTP server.
The Delivery tab also provides useful configuration options. On this tab, you can specify retry intervals (the interval at which IIS will send your queued mail when you're working offline).
On the Messages tab, you can restrict the size of messages that your server will relay. On my personal system, I disable all size restrictions because I want my server to send messages regardless of their size.
The final step in setting up your relay server is to configure your client. Regardless of which email client you're using, change the Outgoing Mail or SMTP server to localhost (127.0.0.1). Then, whenever you change between dial-up and network connections, you'll be able to send email without worrying about changing your outbound SMTP server.