The trailing '.' makes the name into a "Fully Qualified Domain Name", i.e. an absolute domain name.
The trailing dot tells the DNS server that this is a fully qualified name. The dot is the root of the DNS heirarchy. If you don't use the dot, the DNS server will assume that it's a record in the current zone and will append it for you. For example, if you have a CNAME in exmaple.com that points to host.example.org, when you query for that, you'll get host.example.org.example.com, which probably isn't what you wanted.
In Bind config files if you don't add the trailing '.' then the name is assumed to be relative to the current zone file's
REFERENCES
http://serverfault.com/questions/18113/dns-trailing-periods
The trailing dot tells the DNS server that this is a fully qualified name. The dot is the root of the DNS heirarchy. If you don't use the dot, the DNS server will assume that it's a record in the current zone and will append it for you. For example, if you have a CNAME in exmaple.com that points to host.example.org, when you query for that, you'll get host.example.org.example.com, which probably isn't what you wanted.
In Bind config files if you don't add the trailing '.' then the name is assumed to be relative to the current zone file's
$ORIGIN.$ORIGIN example.com.
mail IN A 192.168.1.1
mail2 IN A 192.168.1.2
server IN A 192.168.1.3
@ IN MX 10 mail ; not FQDN - example.com. appended
IN MX 20 mail2.example.com. ; FQDN
IN MX 30 mail.example.net. ; FQDN in another domain
IN MX 40 mail2.example.net ; ERROR - not FQDN - example.com appended
www IN CNAME server ; not FQDN - example.com. appended
REFERENCES
http://serverfault.com/questions/18113/dns-trailing-periods
