MX record
An MX (Mail Exchange) record is a DNS entry that tells other mail servers which server is responsible for receiving email on behalf of a domain. Each MX record has a priority value -- lower numbers are tried first -- so a domain can list a primary mail server and one or more backups. Without a correct MX record, incoming mail to that domain has nowhere valid to go and will bounce or queue indefinitely. MX records point to a hostname, not an IP address directly, so that hostname's own A/AAAA record also has to resolve correctly for mail delivery to actually complete.
By AdminKit team, Netbase JSC · Updated