I think both answers haven't gotten at the true problem here... the problem
is not in configuration at all. The issue is that even when properly and
totally configured, the autodiscover service is polled (if it is the same as
Outlook 2007 -- once per hour) and this information is used to locate
free/busy etc. When the client cannot find this information in DNS, and
without a mechanism to locally override the autodiscover resolution process
and point the client at a particular server for autodiscover operations, this
process fails, thus causing free/busy, configuration of out of office
messages, delegate operations, and availability in meeting requests to fail.
I have seen no place in the user interface nor a file location nor a
scripting parameter in Entourage 2008 to configure the override domains and
specify the XML. Take a look at
http://exchange-genie.blogspot.com/2007/07/autodiscover-ad-attribute.html
under the section "deploying an xml file" -- this is what I (and likely
others) need to be able to do, specify the domain with the local location of
the file, and the xml in the file, and the option to prefer the local vs the
network attempt.