Adding Calendar Permissions in Microsoft 365 and Exchange with PowerShell

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Management of calendar permissions in Microsoft 365 and Exchange Server mailboxes is a common task for email administrators. This tutorial shows how to use PowerShell to list, add, and remove mailbox calendar access on Microsoft 365 (formerly Office 365) and on-premises Exchange Server.

Managing Calendar Permissions with PowerShell

Calendar in a Microsoft 365 and Exchange Server mailbox is a pre-configured system folder that is displayed in a special calendar view in Outlook/Outlook Web Access. Users can manage calendar permissions themselves from the Outlook GUI interface. However, an administrator cannot manage calendar permissions from the Exchange Admin Center or the Microsoft 365 Admin Portal. Administrators use PowerShell to manage user and shared mailbox calendar permissions.

There are several cmdlets in PowerShell to manage permissions for Calendar (and other folders) in an Exchange Server or Microsoft 365 mailbox:

• Get-MailboxFolderPermission – list current calendar permissions;
• Add-MailboxFolderPermission – grant calendar permissions to a user or group;
• Set-MailboxFolderPermission – modify existing permissions;
• Remove-MailboxFolderPermission – remove calendar permissions;
• Get-MailboxCalendarFolder – get calendar folder information.

To manage calendar permissions in mailboxes, you must first connect to your Microsoft 365 or on-premises Exchange Server tenant from the PowerShell console.

Connect to Microsoft 365 (Exchange Online) Tenant with PowerShell

1. Open the PowerShell console;
2. Check if the Exchange Online PowerShell V3 (EXO V3) is installed on the computer:

   Get-InstalledModule ExchangeOnlineManagement

   If the module is missing, install it from the PowerShell Online Gallery by using the following command:

   Install-Module ExchangeOnlineManagement -Force

   

3. Connect to your Exchange Online tenant:

   Connect-ExchangeOnline -UserPrincipalName kirill@theitbros.onmicrosoft.com -ShowProgress $true

   

Provide your Microsoft 365 tenant administrator credentials. If you have Multi-Factor Authentication (MFA) enabled for your Azure account, you will need to confirm your account sign-in with your second factor.

Connecting to On-prem Exchange Server with PowerShell

You can remotely connect to your on-prem Exchange Server 2010, 2013, 2016, and 2019 using PowerShell (you do not need to install the Exchange Management Shell on your computer):

1. Save your Exchange administrator’s credentials into the PowerShell variable:

   $LiveCred = Get-Credential

2. Connect to your Exchange server using the Kerberos authentication (replace ny-msg-02 with the FQDN of your on-prem Exchange Server):

   $Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri http://ny-msg-02/powershell/ -Credential $LiveCred -Authentication Kerberos

3. Allow local PowerShell script to run by changing PowerShell Execution Policy to RemoteSigned:

   Set-ExecutionPolicy RemoteSigned

4. Import cmdlets from a remote Exchange Server host to your PowerShell session:

   Import-PSSession $Session -DisableNameChecking

Hint. If you logged on directly to the on-premises Exchange Server host, you can use the Exchange Management Shell or can load Exchange cmdlets with the command:

Add-PSSnapin Microsoft.Exchange.Management.PowerShell.SnapIn

View Mailbox Calendar Permissions with PowerShell

Use the Get-MailboxFolderPermission cmdlet to list the existing calendar permissions of the specified mailbox:

Get-MailboxFolderPermission cyril@theitbros.onmicrosoft.com:\calendar

FolderName User AccessRights SharingPermissionFlags

———- —- ———— ———————-

Calendar Default {AvailabilityOnly}

Calendar Anonymous {None}

The default AvailabilityOnly role is only assigned to a Calendar folder.

Note. By default, users in Exchange Server organizations and Microsoft 365 (Exchange Online) tenants can’t view other users’ Outlook e-mails or calendar items. The only permission that is granted to all users by default is the ability to view the Free/Busy information in other users’ calendars (this is the AvailabilityOnly role).

Note. If this command returns that ‘username:\calendar’ cannot be found, it is most likely that the user has Outlook language settings other than English. Appropriately, the Calendar folder name can be different (calendar\kalender\calendario\calendrier\календарь). For example, to view calendar permissions for the Dutch Language (nl-NL) use the command:

Get-MailboxFolderPermission username:Agenda

You can get the name of the calendar in the current user’s regional configuration with the command:

(Get-MailboxFolderStatistics username -FolderScope Calendar).Identity

List All Mailbox Calendar Permissions in Exchange

You can get the list of all mailbox calendar permissions in your organizationby using the following command:

Get-Mailbox | ForEach-Object {Get-MailboxFolderPermission $_":\calendar"} | Where {$_.User -like "Default"} | Select Identity, User, AccessRights

Find Calendars a Specific User Has Access To

You can find all the calendars in your organization that a particular user has been granted access to. In this example, we want to display a list of user mailboxes whose calendars are allowed to be accessed by a user named Muller:

Get-Mailbox | ForEach-Object {Get-MailboxFolderPermission $_":\calendar"} | Where {$_.User -like “*Muller*”} | Select Identity, User, AccessRights

The list of users whose calendars the user can access is listed in the Identity column. The AccessRights field shows the current calendar permissions.

Understanding Outlook Calendar Permissions

When managing calendar and Outlook folder permissions, you can use the following predefined permissions levels:

• Owner — gives full control of the mailbox folder: read, create, modify, and delete all items and folders. Also, this role allows to manage item’s permissions;
• PublishingEditor — read, create, modify, and delete items/subfolders (all permissions, except the right to change permissions);
• Editor — read, create, modify, and delete items (can’t create subfolders);
• PublishingAuthor — create, and read all items/subfolders. You can modify and delete only items that you have created;
• Author — create and read items. Edit and delete own items;
• NonEditingAuthor — full read access, and create items. You can delete only your own items;
• Reviewer — read folder items only;
• Contributor — create items and folders (can’t read items);
• AvailabilityOnly — read Free/Busy info from the calendar;
• LimitedDetails — view availability data with calendar item subject and location;
• None — no permissions to access folders and files.

You can also use granular permissions to fine-tune the access rights to the mailbox calendar. The following values are available:

• CreateItems;
• CreateSubfolders;
• DeleteAllItems;
• DeleteOwnedItems;
• EditAllItems;
• EditOwnedItems;
• FolderContact;
• FolderOwner;
• FolderVisible;
• ReadItems.

The Permission Level roles described above are just a set of granular permissions. For example, the Editor role is a set of the following individual permissions:

• CreateItems
• DeleteAllItems
• DeleteOwnedItems
• EditAllItems
• EditOwnedItems
• FolderVisible
• ReadItems

Adding Calendar Permissions in Microsoft 365/Exchange Server with PowerShell

In order to grant user2 the permission to view and edit user1 calendar items, run the following command:

Add-MailboxFolderPermission -Identity user1@domain.com:\calendar -user user2@domain.com -AccessRights Editor

If some of the items in the calendar are marked as Private, you can delegate the permissions to view Private calendar items:

Add-MailboxFolderPermission –Identity user1@domain.com:\calendar –User user2@domain.com -AccessRights Editor -SharingPermissionFlags Delegate,CanViewPrivateItems

Note. You can grant access to the mailbox calendar not only for an individual user, but also for a Microsoft 365 group or an mail-enable AD security group.

Yon can assign calendar permissions to a specific user’s calendar in bulk. Simply create a CSV text file containing a list of users you want to grant permission to, and run the command:

Import-Csv users.csv | foreach { add-MailboxFolderPermission -Identity "user1@domain.com:\calendar" -User $_.alias -AccessRights Owner }

In some cases, you may need to allow a particular user (for example, a secretary) to manage all the calendars in the organization:

Foreach ($Mailbox in (Get-Mailbox -ResultSize Unlimited)) { Add-MailboxFolderPermission -identity "$($Mailbox.Name):\Calendar" -AccessRights Editor -User secretary }

You can use the SendNotificationToUser parameter of the Set-MailboxFolderPermission cmdlet to generate a “share invitation” email that summarizes your changes. The option -SendNotificationToUser $true can be used only when you set one of the following permissions via the AccessRights parameter: AvailabilityOnly, LimitedDetails, Reviewer, or Editor. The following command will send a sharing invitation to the user2:

Add-MailboxFolderPermission -Identity user1@domain.com:\calendar -user user2@domain.com -AccessRights Editor -SendNotificationToUser $true

This is what the sharing invitation will look like in Outlook:

You’re invited to share this calendar.
UserName has invited you to view his or her Calendar. Click the Open button above.

How to Change or Remove Calendar Permissions with PowerShell

You can change the Default permissions for the shared mailbox calendar folder and allow all organization users to view calendar items:

Set-MailboxFolderPermission -Identity projects@domain.com:\calendar -User Default -AccessRights Reviewer

Check the current calendar permissions again with the Get-MailboxFolderPermissions cmdlet. They should change:

Get-MailboxFolderPermission -Identity project@domain.com:\calendar

FolderName User AccessRights
———- —- ————
Calendar Default {Reviewer}
Calendar Anonymous {None}
Calendar user2 {Editor}

You can also assign mailbox permissions to the Exchange distribution group, rather than to an individual user:

New-DistributionGroup -Type Security -Name “Resource Calendar Owners” -Alias “grResourceCalendarAccess”

Add-MailboxFolderPermission -Identity user1@domain.com:\calendar -User grResourceCalendarAccess -AccessRights Owner

You can make this bulk calendar permissions change using a simple PowerShell script. To change the Default calendar permission for all mailboxes to Reviewer:

foreach($usermbx in Get-Mailbox  -RecipientTypeDetails UserMailbox) {

$usercalendar = $usermbx.alias+":\Calendar"

Set-MailboxFolderPermission -Identity $usercalendar -User Default -AccessRights Reviewer

}

This will allow all your users to view all the calendars in the organization.

Use the Remove-MailboxFolderPermission cmdlet for removing calendar permissions:

Remove-MailboxFolderPermission -Identity user1@domain.com:\calendar –user user2@domain.com

If you want to reset the user’s calendar permissions to default:

Get-MailboxFolderPermission brett.jackson:\Calendar | % { Remove-MailboxFolderPermission -Identity $_.Identity -User $_.User }

To exclude some “default” permissions entries from the removing script, use the following PowerShell one-liner:

Get-MailboxFolderPermission brett.jackson:\Calendar | ? {$_.User -notmatch "^(Default|Secretary|Anonymous)$"} | % { Remove-MailboxFolderPermission -Identity $_.Identity -User $_.User.ADRecipient.ExchangeObjectId.Guid -Confirm:$false }

Now you can disconnect your PowerShell session from Microsoft 365/Exchange Server:

Remove-PSSession $Session

How to Add a Shared Calendar in Outlook

In order to view other user calendars in Outlook 365/2019/2016 (including room resources, Shared calendars), you should switch to the calendar view and select the calendar type you want to add.

You can select a user from Address Book (Global Address List – GAL), Open Shared Calendar (you should specify user name), Room List, and Internet (web-calendar).

For example, you want to add a calendar from the Global Address List. Find the calendar name you want to add to Outlook and click OK. The shared calendar should appear under the My Calendars in Shared Calendars section.

PowerShell makes it easy to manage user calendar permissions in Microsoft 365 and on-premises Exchange Server environments. While you can’t use the GUI to centrally manage calendar permissions, you can use PowerShell to make bulk changes for for calendar access folder-level permissions.