EXCHANGE Server 2003 (outlook Web access)

Hi all,
1)
i have installed exchange server 2003 in my server.i configure http virtual server.here i have given my host as server name. then it is working fine. if i give another name as host name it is not browsing.

2)when i give FQDN of server name in host name it is browsing as host.domain.com . but i want to access like mail.domain.com.tell me the configuration that meet my requirement.

thank u in advance.