The Wizarding World of PowerShell Calendar Permissions

1. Open the PowerShells and connect to the Exchanges:
   Install-Module -Name ExchangeOnlineManagement
2. Log into the Exchanges:
   Connect-ExchangeOnline -UserPrincipalName <your_username>
3. Take a look at who has access to a calendar:
   Get-MailboxFolderPermission -Identity "Snoop@Dogg.com:\calendar"
4. Give permissions to Martha:
   Add-MailboxFolderPermission -Identity "Snoop@Dogg.com" -User "martha@Dogg.com" -AccessRights Reviewer
5. When you finish, don't forget to close the session:
   Get-PSSession | Remove-PSSession

 Extra Credit:  If you would like to see what rights Martha has to every account in your M365 tenet you can use the command below.  This will take a long time if you have a lot of accounts.

Get-Mailbox | ForEach-Object {Write-Host "Processing mailbox: $($_.PrimarySmtpAddress)" Get-MailboxFolderPermission -Identity "$($_.PrimarySmtpAddress):\calendar" | Where-Object {$_.User -like "martha@Dogg.com"} | Select-Object Identity, User, AccessRights