I've been searching EE for about a week now trying different solutions to this problem and I cant seem to lock it down.
I've migrated Exchange from an old SBS2003 server (still up and running, exchange and all) to a new server running Server 2008 and Exchange 2010.
Everything seems to be working great. Autodiscover checks out fine on all computers. OWA works great. I do not have Outlook Anywhere installed, as I have no users connecting this way. All clients are local and logged into the domain. Also all cell phones are able to connect and send and receive email and calendering works too.
I have client computers that had Outlook 2010 installed before the migration and Free/Busy and Out of Office work fine on. The rest of the clients are running Outlook 2007 and it does not work. Upgrading these stations to Outlook 2010 does not solve the problem either. Most stations are running Window XP and a couple have Windows 7
In IIS if I change EWS to ignore client certificates Free/Busy and Out of Office work just fine, except that it prompts for a password constantly.
I've tried too many things to list but am willing to try any ideas you may have.
Thanks in advance.