A. "MX" ("Mail eXchanger") records are used to specify what are the e-mail servers for the domain. Emails to the domain will be routed to the email server specified as MX record under the domain's DNS. You can enter multiple MX records for a domain to achieve fail over to the next available (secondary) mail servers if the primary MX is not available. To have secondary MX, you assign it a perference number# that is higher than the value for the primary MX. You can also assign the same preference# for multiple MX records to achieve load balancing.
It is easy to find out what are the MXs for a domain. For example, to find out what are the MXs for dnsexit.com, you can use DOS nslookup command as the followings:
C:> nslookup -type=mx dnsexit.com
dnsexit.com MX preference = 2, mail exchanger = mail2.dnsexit.com
dnsexit.com MX preference = 1, mail exchanger = mail.dnsexit.com
You will find there are 2 MXs for the domain. The MX, mail.dnsexit.com, is the primary MX and mail2.dnsexit.com is the secondary MX (only receive emails when mail1 is down).
To setup MX for your domain at DNSExit system, click on "Edit DNS" to enter DNS control panel. You will find the MX section to enter MX for the domain.