Recently we came across an issue where a user (Let’s say user A) reported that few users (Users B, C) have access to his outlook calendar and when he try to remove those users, he is not able to do that.
User A tried clicking on “Share my calendar” in Outlook then, permissions tab, then clicked on the user B & C that he wanted to remove, clicked on remove, it went away, then as soon as user A hit apply, User B & C come right back up with Reviewer rights.
We checked out if there is any delegation set for the user A’s mailbox and there was no delegation.
So where are these permissions, These permissions are in AD, somewhere deep inside. The user A was part of several security groups as well as the users B & C. So tracking down those permissions was a tedious task and being a pure messaging guy I was not supposed to play with AD unless necessary.
So what’s next, Lets troubleshoot calendar permissions using PFDAVAdmin. That’s really an amazing tool to see the permissions on metadata of your mailbox.
Below is the step by step procedure to reach the calendar permissions for any user mailbox.
1. Run PFDAVAdmin.exe, enter Exchange Server name/IP, Global Catalog name/IP and authentication, and connect to all mailboxes (Remember it is not public folders)
2. Now Expand the mailboxes, and go to the specific mailbox (User A) having permissions issue. Mailboxes are sorted by distinguished name.
3. Expand the affected mailbox (Mailbox for user A) , expand, Top of Information Store and select Calendar.
4. Right click on Calendar, Select “Folder Permissions“. A new Window will open, where you can see all permissions on the Calendar of the user. Select unwanted users (User B & C) and remove, then click commit changes.
5. We are done 
