Differences Between the Etrn and Sbsetrn Commands (250045)

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Etrn

The etrn command is an extended Simple Mail Transfer Protocol (SMTP) e-mail dequeuing command that is issued to an e-mail host for Internet e-mail retrieval. The etrn command requires a static TCP/IP address and valid MX and A records that are registered within Domain Name System (DNS).

Sbsetrn

The sbsetrn command is available with Small Business Server (SBS) 4.0 and 4.0a. You can specify the sbsetrn command as a custom command within the e-mail retrieval properties located on the Dial-Up Connection tab of Internet Mail Service, when used in conjunction with the Microsoft ISP Resource Kit and Microsoft SBS-aware Internet service providers (ISPs). To manually apply the sbsetrn command in SBS 4.5, click the link to the following Microsoft Knowledge Base article: Your ISP must have the ISP Resource Kit installed for the sbsetrn command to be valid. The sbsetrn command registers a unique NetBIOS name that the Microsoft ISP Resource Kit provides upon registration with your ISP's Windows Internet Naming Service (WINS) server. This is necessary because the ISP assigns a dynamic Internet Protocol (IP) address to the SBS Microsoft Exchange Server computer when you connect using a dial-up connection. After the IP address is registered with the WINS server, the etrn command is issued the same way and no functionality is lost. The SMTP server queries DNS (in this case an internal DNS server that points to WINS instead of holding the records). When the SMTP server receives the destination, it sends the e-mail message. After you close the connection, the Exchange Server computer then has the ability to remove the name of the WINS server or mark it inactive until the registration takes place again at the next connection interval.