One my Outlook i delegatedfor someone by Tools > Options > Delegates and press the 'Add' button. On the other user's outlook I did File > Open > Other User's Mailbox, picking your mailbox to open.
It was working fine. Other user was able to check my mails but now it says cannot open mailbox when the other user tries to access my mail. I have unplugged my computer from network , can this be a problem.