An MX Record (also called Mail eXchange record) is the DNS record that determines to what server the e-mail should be delivered, that is sent to that domain.
The MX record contains the hostname of a computer/server that will handle the e-mail sent (not the IP address!), and a matching priority or preference. The hostname that is entered in the MX record, has to be an A-record that refers to the correct IP address.
By using the priority in the MX record, you can specify a backup e-mail server that should be contacted, in case the first e-mail server is unable to accept the e-mail. The mailserver with thelowest priority will be contacted first, followed by the mailserver with the 2nd lowest priority, and so on. If two mailservers share the same priority, they will be placed in load balancing. If one server is too busy to accept the e-mail, the mail will be delivered to the 2nd server – and vica versa.
How can I find out what MX records are active for a certain domain?
Go to Start, Execute, and enter “cmd” (without quotes)
Press enter, and the Windows Command Prompt will open. This is a black window, which allows you to enter certain commands.
Enter the following command: “nslookup”.
A new line is shown, where you can enter the following command: “set type=mx“.
Through the command you have just entered, you give the order to check for the MX record, in stead of the default A/CNAME record. After you have pressed enter, a new line will be shown where you can enter the domain name to be queried.
If you press enter now, a new search will be conducted for the MX record (set type=mx), for the domain “nucleus.be”. The result should look similar to the image blow:
Let’s analyse this result, for a second:
Under “Non-authorative answer” you will see 2 lines. These are the 2 MX records that were found for that certain domain. You will see that for the domain “nucleus.be” that there is an MX record, with preference (=priority) 10, that refers to the hostname “asav01.bru.nucleus.be”, and an MX record with the same priority that refers to “asav02.ant.nucleus.be”. If one of the mailservers cannot be reached, the other one will be tried.