Just a simple query

User A has access to User b's Mailbox

User A has access to User c's Mailbox

User D has Access to User A's Mailbox

When User B wants to access User D's Mailbox We have setup the permission but User b cant open the User D's Mailbox in outlook. Then we have added User D's Email in Outlook separately but now User B can See User A and User C Which user B  shouldn't see.

This is just getting in riddle. Any idea how to solve

Based on your description, it appears to be a bug. Suggest open a ticket with MS Premier for troubleshooting.

In my experience with these unexplainable events, it's sometimes easier to remove all permissions and create them again from the beginning.

Hi,

First of all, delegate permissions are not inherited. So User B should have seen User A and User C. Secondly, Microsoft recommend to configure Outlook with one Exchange account. If there are multiple Exchange accounts configured in one Outlook client, we will meet some situation like this problem or other problem.

Anyway, how many accounts you configured in one outlook client?

Please consider the following situation:

User B and User D are in the same Outlook client (same profile), you log in outlook with User D account. User D has Access to User A's Mailbox. Auto-Mapping feature will add User A as additional Exchange account automatically. Even User D logged in outlook separately, User B can also see User A in outlook because they are in the same profile. If there are more than two Exchange accounts in the same outlook, the situation will be more complicated.

So please try to remove these permissions first and add user in outlook separately to check this problem.

Best Regards.