With the combination of Outlook 2007 and Exchange 2007, several new services have been introduced which are designed to simplify the end-user experience, although there are “gotchas” to be aware of. These features are called AutoDiscover, AutoConfigure, and the Availability Service.  The latter two are built around the first.

AutoDiscover is an XML-based service used by the client to locate and connect to other web-based Exchange services, including AutoConfigure, Availability Service, and Exchange Web Services (a new API for programmatically accessing Exchange).  The client (which can be Outlook 2007, Windows Mobile, the upcoming Entourage EWS, or an EWS-based program or script) passes the user’s e-mail address and credentials to the AutoDiscover service as a SOAP query (after first checking to see if the desired information is available in Active Directory). If the credentials are valid, and depending upon the type of request, AutoDiscover will pass back a SOAP response with the requested information, such as what server the client should be configured to point to, the URL for downloading the Offline Address Book, the URL for Exchange Web Services, or the URL for the Availability Service.

AutoConfiguration is an Outlook 2007 feature which uses the AutoDiscover service to configure the Outlook profile (if the user chooses not to configure their profile manually).  There are several caveats to be aware of:

1. By default, AutoConfiguration will set the Outlook profile to cached mode, which we don’t generally recommend for our clients.  Cached mode and been known to cause major problems such as inconsistent views of shared calendars and mailbox data loss due to corruption of the OST.
2. The upcoming Entourage EWS (which is currently in beta) adds autoconfiguration functionality, but returns the name of a specific domain controller for the directory server (rather than the directory.austin.utexas.edu NetScaler alias).  This is problematic for off-campus users, as the DCs are not routed off-campus.
3. When attempting to perform an autoconfiguration, the client will parse the e-mail address provided by the user and use that to construct an address to query for the AutoDiscover server (assuming that it cannot pull this info from the Service Connection Point in Active Directory).  For example, for username@mydomain.com, the client will look for the AutoDiscover service at autodiscover.mydomain.com. However, suppose that the mydomain.com Exchange server is hosting another SMTP address space, such as for an acquired company.  In this example, the user’s e-mail address is username@otherdomain.com.  The client will look for the AutoDiscover info at autodiscover.otherdomain.com.  For this scenario, either the user should  specify a “mydomain.com” address, or the network admins should add a CNAME entry to DNS pointing autodiscover.otherdomain.com to autodiscover.mydomain.com.

The Availability Service is a SOAP/XML mechanism by which Outlook 2007 retrieves free/busy information from the Exchange server.  The client uses the AutoDiscover service to locate the SOAP URL for the Availability Service, then uses SOAP queries to pull the relevant free/busy information.  This is all well and good except for one fundamental design flaw in Outlook 2007.  For authenticating against the Availability Service, Outlook uses the credentials that were used to login to the workstation, not those provided for mailbox access.  This is problematic for client systems which are not joined to the domain.  The only workaround is to join the client to the domain.  For off-site usage, this generally requires using a VPN service to join the system to the domain and to authenticate, even though the Availability Service itself simply uses web protocols.