An MX record tells senders how to send email for your domain.
When your domain is registered, it’s assigned several DNS records, which enable it to be located on the Internet. These include MX records, which direct the domain’s mail flow. Each MX record points to an email server that’s configured to process mail for that domain. There’s typically one record that points to a primary server, then additional records that point to one or more backup servers. For users to send and receive email, their domain's MX records must point to a server that can process their mail.