Secondary Mail Server MX Record
Whenever I come across an issue that I think will be helpful to know, I feel I should write it down. I like to know that I can always come back to my website and find my notes.
So I have this project where we are changing ISP’s and thus getting a new IP address for their mail server. In order to upgrade smoothly we need to make some DNS changes for the mail server. We will add the new IP address as a secondary mail server, and then we can change the ISP. Here is an example of what to do with the DNS MX records.
Before;
mail.yourcompany.com A 1.2.3.4
yourcompany.com MX 10 mail.yourcompany.com
Now Make it look like this;
mail.yourcompany.com A 1.2.3.4
yourcompany.com MX 10 mail.yourcompany.com
newmail.yourcompany.com A 2.2.2.2
yourcompany.com MX 20 newmail.yourcompany.com
The reason we are doing this is because DNS can take up to a day to populate through all the DNS servers in the world, and this will allow your mail to continue to work during the upgrade. After one day change your DNS to;
mail.yourcompany.com A 2.2.2.2
yourcompany.com MX 10 mail.yourcompany.com
