The Exchange Availability Service allows Outlook 2007 and Outlook 2010 clients to retrieve Exchange free/busy information...
through Exchange Web Services. Unfortunately, connectivity problems happen and Exchange 2010 free/busy information doesn't always display as it should. Here are four areas to check -- and two tools to consider -- when free/busy stops working.
1. Check the Exchange Autodiscover service
Outlook 2007 and Outlook 2010 do not use public folders to retrieve Exchange 2010 free/busy information. Instead, they use Exchange Web Services (EWS). The EWS URL is handed to your Outlook 2007 or Outlook 2010 clients via the Autodiscover service. This is also true for other Exchange servers in partner organizations that wish to share information through federation.
If Exchange 2010 free/busy info isn't working, the first thing you should check is the Autodiscover service. If you work with external users or partners, you'll need an entry in your public domain name server (DNS) zones to check Autodiscover. It's usually a host record such as "autodiscover.<your domain>.com." This record resolves to your client access server (CAS) infrastructure, but service records are also used quite often.
The Autodiscover service is found by Outlook clients when querying the service connection point (SCP) object in Active Directory. The SCP is set up when the CAS server role is installed, but you should still validate that it is working correctly.
2. Check client access server URL settings
Each CAS service URL has two properties: internal and external. No matter which you use, make certain that the URL defined for EWS is accessible. The EWS URL settings are only manageable through the Exchange Management Shell.
Check the settings using the following line of code:
Get-WebServicesVirtualDirectory | fl name,*url*
Make sure that any FQDNs that have been set are resolvable via DNS. You also can modify the internal and external URL values if they're incorrect. Simply enter the Set-WebServicesVirtualDirectory cmdlet.
3. Check your certificates
The self-signed certificates that are installed along with Exchange 2010 are not sufficient for production use. Therefore, when troubleshooting Exchange 2010 free/busy issues, be certain that the certificates your clients and external partners will trust are installed on your CAS servers. Make sure they're also assigned to the IIS.
Additionally, be sure that the certificates are not only issued by a trusted source, but that you have also added the correct namespace(s) to the certificate subject and subject alternate names. This guarantees that clients and partners who make secure connections to the availability service via SSL don't encounter any issues and can see all necessary free/busy information.
4. Check firewalls and reverse proxy
Because EWS is a Web service, clients need to access it through a firewall. Connections to EWS are secured via SSL, so check that TCP port 443 to your CAS is allowed through your firewall.
In addition, if you're publishing your CAS to the Internet via a reverse-proxy solution, you must have a publishing rule that allows access to the /EWS/* path on your CAS server(s).
5. Test email AutoConfiguration
Whether you're troubleshooting Exchange 2010 free/busy lookups internally or externally, both Outlook 2007 and Outlook 2010 have a built-in tool that can help. To access it, open Outlook and then hold down the Ctrl key and right-click the Outlook icon in the system tray.
This launches the Test E-Mail AutoConfiguration utility. Enter an email address -- and password if testing from the outside -- and click Test. Assuming that the Autodiscover service is contacted, you will receive the Autodiscover response, which includes the EWS URL.
6. Run the Exchange Remote Connectivity Analyzer
If troubleshooting Exchange free/busy information with external partners or clients, you can also turn to the Exchange Remote Connectivity Analyzer (ExRCA). ExRCA includes a number of tests, but since we're troubleshooting free/busy problems, we want to use the Synchronization, Notification, Availability, and Automatic Replies test.
To begin, provide the name and password for a mailbox within your Exchange 2010 organization. Don't worry, the password is not cached and is only used for testing purposes. You can also use ExRCA to locate the availability service via Autodiscover.
Once logged into the mailbox, the tool attempts to create and delete items in an effort to test synchronization functionality. Therefore, you need to perform the test on an empty test mailbox. A number of calendar items will be created and free/busy access will be validated. If the test encounters any problems, it describes exactly what's causing the problem.