Issue Description/ scenario: User mailboxes have been migrated from a legacy Exchange version (exchange 2003) to a current version, they can access all other features, but unable to view their free/busy information or see other user Mailboxes free busy information, but they are able to see the FB information for mailboxes created in the new mailbox server:

Figure 1:



Root cause:  Exchange 2003 publishes free/busy information on public folders' system folders, while Exchange 2007/2010 can use both public folder and the availability service. Public folders in 2007 are kept for legacy Outlook (Outlook 2003) users, as Outlook 2003 does not have Availability services compatibility.
Now for some reasons, if the system folders were not migrated properly, this issue is inedible and or the First Administrative Group was deleted (ABSOLUTELY NOT RECOMMENDED).
Now, if this be the scenario, the PF hierarchy will be shifted to the Exchange Administrative Group (in 2007/2010,2013)

Note: Migration from exchange 2003 to 2013 is not possible unless Exchange from 2003 has been migrated either to 2007 or 2010 [FYI]

System folders view in exchange 2003 :

Figure 2:




Availability service snapshot :

Figure 3:


Image taken from TechNet 

 Now, legacy Outlook users will look for their free busy information and get the information as unknown, as shown in Figure 1.
using 

The next logical step the user will perform is to clear the free/busy cache by running Outlook with the /cleanfreebusy switch.  

The next logical step would be to do a send/receive to sync the cached Outlook with the server , where the user will get the following error "

Figure 4:




Upon Viewing the Event Viewer the user will get the following event 8207 stating:

Event ID : 8207 
Raw Event ID : 8207 
Record Nr. : 6 
Category : General 
Source : MSExchangeFBPublish 
Type : Error 

To resolve the issue, the first mandate is to have Public folder databases in the newer version of exchange (Which is Obvious)

If you check the legacyExchangeDn attribute, it will point to the first administrative group for the migrated users .

Now the Thing about LDN or legacy Exchange Dn , is it is created during the birth of the object(mailbox in this case), and does not get modified , even if the user is migrated to a newer version, i.e. Exchange Administrative group ,instead of First Administrative group.

Thus the migrated users will have the LDN as First Administrative group.

Coming back to the resolution, check that the free/busy folder exists in the new version .

This can be done by running the command :  get-publicfolder “\non_ipm_subtree\schedule+ free busy” -recurse 

Figure 5:




Now the resolution lies in creating a new folderative group.

Thus the migrated users will have the LDr for the "First Administrative Group" under the "\non_ipm_subtree", which btw , is the technical term for system folders.

This can be done using the cmdlet :

new-publicfolder -name “EX:/o=mojorisin/ou=First Administrative Group” -path “\non_ipm_subtree\schedule+ free busy”
Note:mojorisin is my org name . Change the Orgname according to your Organization.

Post this , recreate a Outlook profile for a legacy moved mailbox and do a send receive. 

The user should be able to view the free/busy information now.

Cheers 

Max