The MX record sets the mail server for your domain name, directing all emails to the correct location and mail server.
If you have your-domain.com, setting an MX record will determine where the mail for email@your-domain.com is sent. The mail server must be configured to accept email for the domain.
By default, your domain names will have an MX record pointing to the mail. subdomain (for example, mail.your-domain.com). When you set up your mailbox in your email client, you will be able to use mail. as your incoming and outgoing server. Your username will be the mailbox name, and your password will be the mailbox password.
If you wish to use a different mail server, you can change the MX record in ‘Manage DNS’ in your eXtend or Domain Control Panel.