redirtect web address to a DMZ address

hello
ok, so we recently moved a unix box to the DMZ, we can access it by using the ip address, but if you type the name in the address bar, it doesn’t connect.

i already changed the mx and dns records for the outside interface and it works.

my question here is, hot to do a url redirection, i mean, how to tell the Firewall: when somebody with an internal ip tries to get to this.webserver.com, send him to 10.80.6.6 (not real ip)
i have an ASA 5500