Just had to give one of our helpdesk guys a quick run down on mx records and how to find them .. I thought I would just add it on here in case someone needed to know how to do it (on a Windows machine)
An MX record or Mail exchanger record is a type of resource record in the Domain Name System (DNS) specifying how Internet e-mail should be routed using the Simple Mail Transfer Protocol (SMTP). Each MX record contains a preference and a host name, so that the collection of MX records for a given domain name point to the servers that should receive e-mail for that domain, and their priority relative to each other.
To find an MX record on a Windows machine with nslookup
1. Open a DOS 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. For an example, type "hotmail.com".
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".