On Windows, when delegated access to another mailbox, Outlook can begin to perform poorly depending on the number of mailboxes attached to your account, the available disk on your computer to store mailbox data and the perfrormace of your PC.
To try to improve performance if you have a large number of mailboxes delegated to you, or the delgated mailboxes are very large in size, turn off caching of shared folders in Outlook.
To do this:
- Open Outlook, then click File.
- Click Account Settings and choose Account Settings...
- In the Account Settings window, in the Email tab, double click your mailbox account.
- Click More Settings.
- In the Microsoft Exchange windows, click the Advanced tab, then uncheck Download shared folders. Click OK.
- Click OK, Done, Next and Close to all open setting windows. Exit Outlook and start it again.
Shared folder within mailboxes will not download content to your computer. You will need a constant internet connection to access resources other that within your mailbox.