Outlook 2010 on Exchange 2003: Will Free/Busy work?

Outlook 2010 is already a second generation of Microsoft Exchange clients that’s now using new Availability-based Free/Busy technology. How does it handle Legacy F/B in pure Exchange 2003 environment? There is not much information on the Web or TechNet about it (or at least I wasn’t able to find definitive answer) so here I wanted to share my findings and fill this gap.

With Outlook 2007 we could have forced it to talk to Ex 2003 legacy F/B in PF but Outlook 2010 (or 2013) no longer honors this: https://support.microsoft.com/kb/982698

“The UseLegacyFB registry value is not used by Outlook 2010 or Outlook 2013.”

However Outlook 2010 is smart enough to sense Exchange 2003 environment and defaulting to Schedule + F/B Public Folder based technology. It makes it less flexible if for example you have Exchange 2007/2010 environment with many Outlook 2003 clients and need to force it to go to the Public Folders just like Outlook 2003 does or Outlook 2007 with UseLegacyFB registry key. However on Exchange 2003 it just works (see my screenshots below)! I assume this was another logical step where Microsoft de-emphasized the legacy F/B technology with Exchange 2013 removing it completely.


Performing Autodiscover Test on Outlook 2010 – of course it fails to retrieve any data when connects to Ex 2003!


Legacy F/B messages created by Outlook 2010 SP2 in Ex 2003 Schedule + F/B PF (was completely EMPTY at first)


F/B data viewed by organizer in Outlook 2010 Scheduling Assistant


To speed up legacy F/B effects in my LAB, I had to change this Outlook 2010 setting from 15 to 1 min