What’s an MX Record?

MX stands for Mail eXchange. MX Records tell email delivery agents where they should deliver your email. You can have many MX records for a domain. They provide a way to have redundancy and ensure email will always be delivered.

Google Apps provides a common example of using MX Records to deliver email. When you create a Google Apps account and you want your email to be delivered to your Google Apps mail account, Google provides a set of MX records you need to add to DNSimple. Here are the default MX records Google suggests:

• aspmx.l.google.com 1
• alt1.aspmx.l.google.com 5
• alt2.aspmx.l.google.com 5
• aspmx2.googlemail.com 10
• aspmx3.googlemail.com 10

Google provides you with 5 different servers that can accept your email. Each MX record includes a priority value, which is a relative value compared to the other priorities of MX records for your domain. Addresses with lower values will be used first. Therefore, when a mail agent wants to deliver an email to you, it would first attempt to deliver to aspmx.l.google.com. If that server can’t handle the delivery, it would move onto alt1.aspmx.l.google.com. If that server can’t handle the delivery, it would move onto alt2.aspmx.l.google.com, and so on.

MX records make it easy to define what servers should handle email delivery. They allow you to provide multiple servers for maximum redundancy and ensured delivery.