One of our users wants to share a Microsoft outlook subfolder with his colleague he does not want his colleague to have access to inbox just the subfolder. We are using exchange 2007 server. 

Hi,

In order to share Outlook subfolders with another user, you need to give them the desired permission (at least Reviewer) to the folder and at least Folder visible permission to every folder above the shared subfolder (including the root folder, which is the folder you click on to display Outlook Today).

If he doesn't want the colleague to have access to his Inbox, just set the permission as None, tick the option "Folder visible":

Then let the colleague add his mailbox as an additional mailbox from the Account Settings, the colleague should only be able to view the content in the subfolder.

Regards,

Melon Chen
TechNet Community Su