Can't Access Shared Mailbox

Occasional Visitor



One of my employees is unable to access our shared mailbox. We added them from the admin center but when clicking on the new mailbox, after loading for a while, this error message appears:


"Cannot expand the folder. This set of folders cannot be opened. C:\Users\(our domain)\AppData\Local\Microsoft\Outlook\(employee email)\.ost is in use and cannot be accessed. Close any application that is using this file and then try again. You might need to restart your computer."


We've restarted several times with no luck. 


Any advice?

1 Reply


It can take several hours for a user's permissions to be applied to a Shared Mailbox. If you have waited several hours (I'd recommend at least 6 if not more) then I would try:

  1. Turn off user's permissions to Shared Mailbox.
  2. Wait 4 - 6 hours
  3. Turn on user's permissions to Shared Mailbox.
  4. Wait 4 - 6 hours
  5. Have user try to access Shared Mailbox