domain name system - CNAME rule being ignored

On a server with Plesk installed I have added a CNAME rule pointing from one of the sites subdomains to an external website.

I have checked the named configuration for that domain name and it shows the CNAME however the sub domain just points to the default server page and ignores the CNAME rule. Named has been restarted and I've also run the rvmng reconfigure-vhost command.

I edited another server to test this, on cPanel, and it works fine.

The conf file for the domain:

; *** Ts file is automatically generated by Plesk ***
$TTL    86400


@       IN      SOA     ns.example.com. cf.example1.com. (
                    1292946742      ; Serial
                    10800   ; Refresh
                    3600    ; Retry
                    604800  ; Expire
                    10800 ) ; Minimum

example.com.             IN NS   ns.example.com.
ns.example.com.          IN A    xx.xxx.xxx.xx
example.com.             IN A    xx.xxx.xxx.xx

webmail.example.com.             IN A    xx.xxx.xxx.xx
mail.example.com.                IN A    xx.xxx.xxx.xx
beta.example.com.                IN A    xx.xxx.xxx.xx
ftp.example.com.                 IN CNAME        example.com.
www.example.com.                 IN CNAME        example.com.
login.example.com.               IN CNAME        socialize.gigya.com.
example.com.             IN MX  10 webmail.example.com.

You can see the CNAME rule in the file but it just gets ignored?

Thanks in advance for any help.

EDIT: I just noticed that the site's nameservers aren't on this server but the default doteasy ones so I assume that may be why the rule is ignored. I will change the nameservers and see if that solves it. I'll update here with the outcome. Thanks guys for your tips so far.

EDIT 2: The server only has one IP address so it won't be possible to use custom name servers. Could this be the cause though? When I run dig cname login.example.com it returns:

; <<>> DiG 9.7.1-P2 <<>> cname login.example.com
;; global options: +cmd
;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20919
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;login.example.com.     IN  CNAME

;; AUTHORITY SECTION:
example.com.        3600    IN  SOA dns7.doteasy.com. hostmaster.doteasy.com.     2010070101 3600 1800 86400 10800

;; Query time: 258 msec

;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Tue Dec 21 20:37:22 2010
;; MSG SIZE  rcvd: 95

I take it this is why the CNAME is being ignored? As the DNS isn't actually hosted on our server?

UPDATE The issue was solved, offsite DNS was why the rules were ignored. Thank you all for your help.

Answer

did you try using dig ?

dig cname example.com 

I understood that dig would give an answer if something is configured in the ANSWER SECTION

EDIT
Instead of the CNAME, I think it should be an A record than a CNAME record.

For example: Look at how to redirect your domain name to Tumblr and have them host your blog . I am assuming you are trying to do the same here