How to Use Telnet to Ensure Internet Accessibility
Topic Last Modified: 2005-05-20
If servers on the Internet cannot reach your mail server, you cannot receive Internet mail. You can use telnet to verify that your mail server is accessible by other servers on the Internet.
After you verify that your MX records are set up correctly, you can then verify that other servers on the Internet can access your Exchange Server.
To verify that other servers on the Internet can access your Exchange Server, from a location outside of your intranet, use telnet to connect to your mail server on port 25. To validate connectivity when you connect, you must use a computer that has direct access to the Internet. If the server has multiple network interface cards (NICs) or IP addresses, you must use telnet to connect to the Internet-facing IP address.
Before you perform the procedure in this topic, read Verifying DNS Design and Configuration.
At a command prompt, type telnet <your mail server> 25, and then press ENTER.
Verify that you receive a response similar to the following, which shows the results of a telnet session to the mail server for Contoso, mailbox.contoso.com.
C:\> telnet mailbox.contoso.com 25 220 corp.contoso.com Microsoft ESMTP MAIL Service, Version: 5.0. 2195.1600 ready at Tue, 5 Sep 2002 11:52:36 -0400