Adding the Other Users folder should not effect opening an attached inbox to this users Outlook profile. If you want the user to have Full permissions you will need to do the following...
- Open ADCU (Active Directory)
- Find the user that you need access to their mailbox
- Double click the user to open properties
- Go to the Exchange Advance Tab
- Click Mailbox Rights button
- Add the user trying to open the mailbox from his Outlook profile
- Give the user full control over the mailbox
- Click Apply and OK
-If you want to add Send on Behalf or Send As do the following...
Send on Behalf
- Open the users properties of the mailbox you want to send on behalf of
- Click on Exchange General Tab
- Click the Delivery Options button
- Under Send on Behalf of, click Add button and add the user to this account
Send As
- Open ADUC
- Click View, Advance Features
- Find the account of the user you want to Send As
- Click the Security Tab
- Add the user and scroll down and select Send As
- Click Apply and OK
Now try expanding the mailbox from the Other users outlook profile. Should have no issues.
If you want to Send As make sure that you use the FROM: in the New email message window and type in the users name.
Hope this helps~!