If you have shared mailboxes open, you must also determine how they are opened, such as being opened manually as an additional mailbox or being opened because of AutoMapping.Ī shared mailbox appears below your own mailbox in the Folder Pane, as shown in the following screenshot.Ī shared folder appears below Shared, such as Shared Calendar or Shared Contacts, as shown in the following screenshot. To do this, you must first determine whether you have shared folders or shared mailboxes open. Reduce the number of shared folders or mailboxes that you have open in Outlook. However, a faster computer that has a smaller mailbox and a fast network connection may be able to open 10 or more shared folders or mailboxes. A computer that has slower hardware, a large mailbox, and slow network connection may not be able to open more than five shared folders or mailboxes. The number of shared folders and mailboxes that you can have open without issues depends on several factors, including hardware, mailbox size, size of the shared folders or mailboxes, number of folders in a shared mailbox, item count in folders, and network speed. In the case with a shared calendar, modifications or additions cannot be made until the program is finished syncing updates. You have many shared folders or mailboxes, or both, open in Outlook. See the folder owner or your administrator to change your permissions.

Right-click the folder, then click Properties to check your permissions for the folder. You don't have permission to create an entry in this folder.

Additionally, when you make changes or additions to a calendar, you may receive the following error message: When you start Microsoft Outlook, switch folders, or synchronize email, you may experience slow performance.

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