Mail Exchange Records (MX) contain a list of mail exchange servers that are to be used for the domain.
An MX record consists of the following four fields:
Host - The domain name of your mail recipient’s email addresses (that is, the portion after the @ symbol in the email address).
Goes To - The FQDN of the mail host. The host must have a valid IP address and cannot point to a CNAME (alias).
Pref - A preference integer value between 0–999 that indicates which mailer to use. The preference value is only relevant in comparison to other MX records' values. Lower values have higher priority.