Going to you’re My Profile site should show your availability based on your Exchange Calendar. However, there are instances when this isn’t displayed. Of course, if you aren’t looking for it, you probably aren’t seeing this feature fail. What would happen is that you open you’re my Profile page, then a Section appears called Availability, and it says, Checking Free/Busy…but then disappears. If you check your ULS logs during this time, you will probably notice the following error (where DOMAIN is equal to your domain):
ExchangeAutodiscover-GetAvailabilityUrl threw an exception: System.Net.WebException: The remote name could not be resolved: 'autodiscover.DOMAIN.com'
The problem seems to be that SharePoint is literally looking for autodiscover.domain.com rather than the actual exchange outlook web access site. A quick fix that I am using is to create a redirect in the DNS which point autodiscovery.domain.com to the Outlook Web Access site, something like owa.domain.com. I’m not sure why this problem occurs, but the redirect works like a charm.