What Is an MX Record?

An MX (Mail Exchanger) record is a type of DNS (Domain Name System) record that tells email servers where to deliver email for a domain.

Think of it as a digital postal address for email — it directs incoming messages to the correct mail servers and determines which server should be tried first if more than one is available. When an email is sent, the sending mail server checks the recipient domain's MX records to determine which server should receive the message.

How MX Records Work

1. Lookup: The sending mail server looks up the MX records for the recipient's domain (e.g., example.com).

2. Priority Evaluation: Each MX record lists a mail server along with a priority value (such as 10, 20, or 30).

   • Lower numbers = higher priority

3. Delivery Attempt: The sending server attempts delivery to the mail server with the lowest priority number first.

4. Failover: If the primary server is unavailable, the sending server automatically tries the next highest-priority server.

This process ensures reliable email delivery even if one server goes offline.

Key Components of an MX Record

• Priority: A numeric value that determines the order mail servers are tried.
  (Example: 10 has higher priority than 20)

• Host/Value: The hostname of the mail server that will receive email
  (Example: mail.example.com)

• TTL (Time To Live): How long other servers cache the record before checking for updates

MxToolbox's free MX Lookup tool lists MX records in priority order for any queried domain. This helpful reference also checks each MX record (IP Address) against 105 DNS-based blacklists.