We have thousands of employees all using MS Exchange. A small percentage of our employees (roughly 5,000) are Mac users. The Mac users that are trying to use Exchange 2007 with Mail.app, Calendar.app and Contacts.app (Mac OS X 10.7 to 10.8) are suffering a number of crippling issues. Mail constantly PWODs (PinWheelOfDeath), seemingly if you just look at it the wrong way. The condition I find most ironic is Mail trying to verify services that cannot possibly be reached when not in the private IP address range of the corproate intranet.(for those not familar, if the Mac has no interface on 10.x.x.x, Mail still checks (and shouldn't) for servers and services on 10.x.x.x which is a non-routeable network address range)
Then there is the Calendar which, once it gets into a mode of error, cannot be recovered without data loss. Case in point, once you get this message below, your local calendar setup is toast and you have little recorse but to delete all of your local calendar data and start over:
Then there is Contacts which cannot accurately search Active Directory for names, returning fewer results than the Microsoft Windows Outlook address book for the same search.
If you want some real fun, bind a Mac OS X Server from 10.4 to at least 10.6.8 to Microsoft Active Directory. Watch DirectoryService in Activity Monitor. At some point, maybe hours maybe months later, you will see Directory Service start to consume vast amounts of CPU resources eventually crippling an 8 processor MacPro. I am dealing with that right at this very moment on a tiny MS Active Directory system handling only 700 (and change) user objects.
While Apple states that they are compatible with MS Exchange/MS Active Directory, the fact of the matter is that they are not. Simple searches across the internet for probelm lists like this reveal that you are lucky to have it working in small enviroments and that is about it. Changes are coming and it is getting better but ...
The only reliable work around at this point is to use the OpenSource DavMail which has much greater MS Exchange compatiblility than Apple has ever mustered. Were I Apple, I would be embarrased enought to hire the DavMail folks and find something else for the Apple MS Exchange compatibility programmers to do :-\
Apple does a lot of things "insanely great" but MS compatiblity, on any level, is not one of them. Abort, Retry, Fail