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, providing a way to have redundancy and ensure that email will always be delivered. MX records make it easy to define what servers should handle email delivery and allows you to provide multiple servers for maximum redundancy and ensured delivery.

How do MX records work?

An MX record is basically an entry in the DNS for a domain, that specifies what email server or computer will handle email for that domain.

Its not uncommon for multiple mail servers to be specified to handle the email for a domain, so each MX record also includes a priority, to determine what order to try each of the mail servers. Multiple mail servers offers robustness and redundancy, to ensure that the email service is always up and running.

What do MX records look like?

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MX records contain the following fields:

  • Name: The domain name
  • Class: This value is always set to IN (which stands for Internet)
  • Type: Always set to MX for MX records
  • TTL: Time To Live. This sets how long in seconds it will take to update the record. A low value means it can be updated quickly, but will increase the DNS server traffic as other servers must check the records more often
  • Priority (or preference): When there are multiple records, mail servers should always try the highest priority server (i.e. the lowest number) first
  • Data: The hostname of the mailserver