Red Hat ENTERPRISE LINUX 4.5.0 Reference Manual page 248

Chapter 12. Berkeley Internet...
In the following example, an
record points the commonly used
server1 IN A 10.0.1.5 www IN CNAME server1
• — Mail eXchange record, which tells where mail sent to a particular namespace controlled
MX
by this zone should go.
IN MX <preference-value><email-server-name>
In this example, the
namespace, giving preference to some email systems over others. The
with the lowest
<preference-value>
servers can possess the same value to distribute email traffic evenly among them.
The
<email-server-name>
IN MX 10 mail.example.com. IN MX 20 mail2.example.com.
In this example, the first
mail2.example.com
domain.
• — NameServer record, which announces the authoritative nameservers for a particular
NS
zone.
This is an example of an
IN NS <nameserver-name>
The
<nameserver-name>
Next, two nameservers are listed as authoritative for the domain. It is not important whether
these nameservers are slaves or if one is a master; they are both still considered
authoritative.
IN NS dns1.example.com. IN NS dns2.example.com.
• — PoinTeR record, designed to point to another part of the namespace.
PTR
records are primarily used for reverse name resolution, as they point IP addresses back
PTR
to a particular name. Refer to
examples of records in use.
PTR
224
record binds a hostname to an IP address, while a
A
hostname to it.
www
<preference-value>
is preferred over the others. However, multiple email
may be a hostname or FQDN.
mail.example.com
email server when receiving email destined for the
record:
NS
should be a FQDN.
Section 3.4, "Reverse Name Resolution Zone Files"
allows numerical ranking of the email servers for a
email server is preferred to the
CNAME
resource record
MX
example.com
for more