Custom MX And A Records

MX Record (Mail Exchange Record) - Mail Server record designating the mail servers that will be handling the mail for a given domain name. When a user has more than one mail servers, the MX records can also specify the order in which the mail servers will be used as primary, secondary, backup, etc.
An A record is a DNS Address resource record. It maps the route of a host name to its address on a server and specifies the Internet Protocol address (in dotted decimal form) of the host. Each host address should have one A record.