Mail Exchange (MX)
records are used to direct email messages across the Internet. An MX record
contains an MX preference that specifies the MX server to be used. The MX
preference values range from 0 through 65536. An MX record contains a unique MX
preference number. You can set the MX preference and the TTL values for an MX
When an email
message is sent through the Internet, a mail transfer agent sends a DNS query
requesting the MX record for the domain name. This query returns a list of host
names of mail exchange servers for the domain, along with a preference number.
If there are no MX records, the request is made for the Address record of that
domain. A single domain can have multiple mail exchange servers.