What is an MX Record?

An MX (Mail Exchanger) record is a type of DNS record that specifies the mail servers responsible for receiving incoming email messages for a particular domain. MX records play a crucial role in email delivery by directing email traffic to the appropriate mail servers.

When someone sends an email to an address like "user@example.com," the sender's mail server needs to know where to deliver the message. The MX record provides this information by specifying the domain's mail exchange servers and their priority.

Here's how MX records work:

1. Priority: Each MX record has a priority value, also known as the preference or preference number. It is represented by a number, where a lower number indicates a higher priority. The priority determines the order in which mail servers should be tried for delivering an email. If the primary mail server is unavailable or unreachable, the next server with a higher priority is attempted.

2. Mail Server: Each MX record contains the hostname of a mail server responsible for handling email for the domain. The hostname is usually represented as a fully qualified domain name (FQDN), such as "mail.example.com."

3. Multiple Records: A domain can have multiple MX records, allowing for redundancy and load balancing. If multiple records exist, the email-sending server will attempt to connect to the servers based on their priority until a successful connection is established.

For example, let's consider the MX records for the domain "example.com":

example.com. MX 10 mail.example.com. example.com. MX 20 backupmail.example.com.

In this case, "mail.example.com" has a priority of 10, indicating it is the primary mail server. "backupmail.example.com" has a priority of 20, serving as a backup mail server if the primary server is unavailable.

When an email is sent to an address within the "example.com" domain, the sender's mail server looks up the MX records for "example.com." It then attempts to connect to the mail servers in priority order, starting with "mail.example.com." If that server is unreachable, it tries the next server, "backupmail.example.com."

MX records are critical for proper email delivery, and configuring them correctly ensures that incoming email reaches the intended recipients in the specified domain.