dns A record , MX record and linux mail server

Dear Experts:

I have installed the zimbra mail server zcs network edition .

Ubuntu host name : orangesrv.mydomain.com after sucesssful installation of split dns and zimbra now it working fine, now i would like to make the webmail accessible like the below
 mail.mydomain.com  (From orangesrv.mydomain.com  to mail.mydomain.com)

Please suggest me how to do this , posted below the /etc/hosts/ and split dns config for your reference.
-------------sudo/etc/hosts------------------------------------
127.0.0.1       localhost.localdomain                   localhost

127.0.1.1       orangesrv.mydomain..com        orangesrv
192.168.1.230   orangesrv.mydomain.com        orangesrv

--------------------/etc/bind/db.mydomain.com---------------------
;

; BIND data file for mydomain.com

;

$TTL    604800

@       IN     SOA    orangesrv.mydomain.com. admin.mydomain.com. (

                         2011051700         ; Serial

                         604800         ; Refresh

                          86400         ; Retry

                        2419200         ; Expire

                         604800 )       ; Negative Cache TTL

;

@               IN      NS      orangesrv
                IN      MX      20 orangesrv
                IN      A       192.168.1.230

orangesrv      IN      A       192.168.1.230

Request you to please check the above config and correct me if anything wrong also please suggest me how to change from orangesrv.mydomain.com to mail.mydomain.com. Please help. Thanks in advance.