An Existing Permission Entry Was Found for User...

While configuring calendar permissions in Exchange Online you may receive the following error message:

An existing permission entry was found for user: Lene.Hau.
    + CategoryInfo          : NotSpecified: (:) [Add-MailboxFolderPermission], UserAlreadyExis...nEntryException
    + FullyQualifiedErrorId : [Server=DB6P189MB0390,RequestId=695957e5-c362-4aab-bd58-af6ab7802dc5,
      TimeStamp=9/26/2021 6:10:19 PM] [FailureCategory=Cmdlet-UserAlreadyExistsInPermissionEntryException]
      F7E2EB7E,Microsoft.Exchange.Management.StoreTasks.AddMailboxFolderPermission
    + PSComputerName        : outlook.office365.com

The error message is thrown when both statements are true:

You try to add mailbox folder permissions with the Add-MailboxFolderPermission CmdLet.
The user/group is already assigned permissions to the mailbox folder.

To modify mailbox folder permissions for an existing user/access right, you must use the Set-MailboxFolderPermission CmdLet (see examples below).

Manage Calendar Permissions Without PowerShell

With Easy365Manager, you no longer need complex PowerShell scripts to manage and modify mailbox calendar permissions.

Easy365Manager provides a user-friendly GUI that admins of any level can use with close to no introduction:

Download your fully functional free trial here.

How to Solve “An Existing Permission Entry Was Found”

Let’s look at a specific example and how to solve it:

The user Lene Hau is already assigned Editor permissions to the mailbox calendar of Tycho Brahe:

PS C:\> Get-MailboxFolderPermission tycho.brahe:\Calendar

FolderName User      AccessRights     SharingPermissionFlags
---------- ----      ------------     ----------------------
Calendar   Default   {LimitedDetails}
Calendar   Anonymous {None}
Calendar   Lene.Hau  {Editor}

You’ll receive an error if you try to grant Owner permissions to Lene Hau with the Add-MailboxFolderPermission CmdLet.

Instead, you must use the Set-MailboxFolderPermission CmdLet:

Set-MailboxFolderPermission tycho.brahe:\calendar -User lene.hau -AccessRights Owner

This command will update the existing permissions assigned to Lene Hau:

PS C:\> Get-MailboxFolderPermission tycho.brahe:\Calendar

FolderName User      AccessRights     SharingPermissionFlags
---------- ----      ------------     ----------------------
Calendar   Default   {LimitedDetails}
Calendar   Anonymous {None}
Calendar   Lene.Hau  {Owner}