How to Find the SMTP Email Server for an Email Address

This example helps determine the mail server for a given email address. This is useful for determining your own SMTP mail server to use with NetMailBot.

If you are unsure of the name of the mail server for an email address, first try "mail.domain.com" or "smtp.domain.com". If niether work, try the following:

    * Requirements
          o Windows 98/Me/NT/2000/XP/2003. Not available for Windows 95.
    * Steps
         1. Open a DOS Command Prompt (Start->Programs->Accessories->Command Prompt)
         2. Type "nslookup".
         3. Your computer's DNS Server name and IP address will be displayed.
         4. Type "set type=mx" - This will cause NSLOOKUP to only return what are known as MX (Mail eXchange) records from the DNS servers.
         5. Type "hotmail.com" or your domain name.
         6. Results returned should look similar to this:

            Server:  ns1.xxx.com
            Address:  192.168.0.1

            Non-authoritative answer:
            hotmail.com     MX preference = 5, mail exchanger = mx2.hotmail.com
            hotmail.com     MX preference = 5, mail exchanger = mx3.hotmail.com
            hotmail.com     MX preference = 5, mail exchanger = mx4.hotmail.com
            hotmail.com     MX preference = 5, mail exchanger = mx1.hotmail.com

            hotmail.com     nameserver = ns1.hotmail.com
            hotmail.com     nameserver = ns2.hotmail.com
            hotmail.com     nameserver = ns3.hotmail.com
            hotmail.com     nameserver = ns4.hotmail.com
            mx2.hotmail.com internet address = 65.54.254.145
            mx2.hotmail.com internet address = 65.54.252.230
            mx2.hotmail.com internet address = 65.54.166.230
            mx3.hotmail.com internet address = 65.54.254.140
            mx3.hotmail.com internet address = 65.54.253.99
            mx3.hotmail.com internet address = 65.54.167.5
            mx4.hotmail.com internet address = 65.54.254.151
            mx4.hotmail.com internet address = 65.54.253.230
            mx4.hotmail.com internet address = 65.54.167.230
            mx1.hotmail.com internet address = 65.54.254.129
            mx1.hotmail.com internet address = 65.54.252.99
            mx1.hotmail.com internet address = 65.54.166.99
            ns1.hotmail.com internet address = 216.200.206.140
            ns2.hotmail.com internet address = 216.200.206.139
            ns3.hotmail.com internet address = 209.185.130.68
            ns4.hotmail.com internet address = 64.4.29.24

         7. Note the first line after "Non-authoritative answer".
            The "MX preference" specifies which mail server to use and in which order. The lower the number, the more preferred the mail server is.

            In this case, since the preferences for each mail server are the same, you can use any of the four "mail exchangers"

source: exclamationsoft.com