Grant Calendar Permissions via PowerShell

Overview

There are scenarios where admins or automation need to grant another user access to a mailbox calendar (read or editor). This post shows safe PowerShell examples for Exchange Online and a bulk flow using a CSV file.

Prerequisites

• An account with the required Exchange admin privileges
• Exchange Online PowerShell module (ExchangeOnlineManagement) or the correct Graph permissions for delegated calendar access
• PowerShell 5.1 or PowerShell 7+ with appropriate execution policy

Connect to Exchange Online

First, install and connect to Exchange Online PowerShell:

# Install if needed
Install-Module ExchangeOnlineManagement -Scope CurrentUser

# Connect interactively
Import-Module ExchangeOnlineManagement
Connect-ExchangeOnline -UserPrincipalName admin@contoso.com

Grant permission to a single mailbox

Grant the user Reviewer (read-only) access on the default calendar folder:

Add-MailboxFolderPermission -Identity 'alice@contoso.com:\Calendar' -User 'bob@contoso.com' -AccessRights Reviewer

To grant Editor (read/write) permissions:

Add-MailboxFolderPermission -Identity 'alice@contoso.com:\Calendar' -User 'bob@contoso.com' -AccessRights Editor

Bulk update from CSV

For bulk operations, create a CSV file with the following format:

Mailbox,Principal,AccessRight
alice@contoso.com,bob@contoso.com,Reviewer
jane@contoso.com,helpdesk@contoso.com,Editor
manager@contoso.com,assistant@contoso.com,Editor

Then use this PowerShell script to process the CSV file:

$csv = Import-Csv -Path .\calendar-permissions.csv
foreach ($row in $csv) {
    try {
        Write-Host "Granting $($row.AccessRight) on $($row.Mailbox) to $($row.Principal)" -ForegroundColor Green
        Add-MailboxFolderPermission -Identity "$($row.Mailbox):\Calendar" -User $row.Principal -AccessRights $row.AccessRight -ErrorAction Stop
        Write-Host "✓ Success" -ForegroundColor Green
    } catch {
        Write-Warning "❌ Failed for $($row.Mailbox) -> $($_.Exception.Message)"
    }
}

Verify and remove permissions

To check existing permissions and remove them when needed:

# List current permissions
Get-MailboxFolderPermission -Identity 'alice@contoso.com:\Calendar'

# Remove a specific permission
Remove-MailboxFolderPermission -Identity 'alice@contoso.com:\Calendar' -User 'bob@contoso.com' -Confirm:$false

Common Access Rights

Here are the most commonly used access rights for calendar permissions:

• Reviewer: Read-only access to calendar items
• Editor: Read, create, modify, and delete calendar items
• Author: Read, create, and modify own calendar items
• Owner: Full access including permission management
• FreeBusyTimeOnly: Can only see free/busy time
• FreeBusyTimeAndSubjectAndLocation: Can see free/busy, subject, and location

Best Practices & Notes

• Always test permissions on a small set of mailboxes before bulk operations
• Use -WhatIf parameter when available to preview changes
• For modern Graph-based automation, consider using Microsoft Graph APIs
• Document permission changes for compliance and auditing purposes
• Regular permission audits help maintain security hygiene
• Consider using security groups instead of individual users for easier management