Force OpenFire to use CNAME

Hey,

I'm trying to figure out how I can get OpenFire to use our CNAME rather than the server name.

Currently a username authenticated against LDAP is:

user.name@abc001.domain.name

Our CNAME is XMPP.domain.name

How can I force OpenFire to allow users to add

user.name@xmpp.domain.name?

Thanks!