preference mail
name {ttl} addr-class MX value exchanger
Munnari.OZ.AU. IN MX 10 Seismo.CSS.GOV.
*.IL. IN MX 10 CUNYVM.CUNY.EDU.
The Mail Exchanger record, MX, specifies a workstation that can deliver mail to a workstation not directly connected to the network. In the first example given here, Seismo.CSS.GOV. is a mail gateway that can deliver mail to Munnari.OZ.AU. Other systems on the network cannot deliver mail directly to Munnari. The two systems, Seismo and Munnari, can have a private connection or use a different transport medium. The preference value is the order that a mailer should follow when there is more then one way to deliver mail to a single workstation. See RFC 974 for more detailed information.You can use a wildcard name containing an asterisk (*) for mail routing with an MX record. Servers on the network can state that any mail to a given domain is to be routed through a relay. In the second example given here, all mail to hosts in the domain IL is routed through CUNYVM.CUNY.EDU. This routing is done by means of a wildcard MX resource record, which states that *.IL has an MX of CUNYVM.CUNY.EDU.