PS export to see if users are sharing their calendar details in Outlook

mdcastorena 

LeonPavesic already supplied an extended example of how you could loop through all mailboxes

Given a CSV file that contains say a list of the PrimarySmtpAddress that you want to check Calendar permissions for, a simple script that would loop through each address might look like:

$mailboxes = Import-Csv -Path <path_to_csv_file>

foreach($mailbox in $mailboxes){
    Get-MailboxFolderPermission -Identity "$($mailbox.PrimarySmtpAddress):\Calendar" -ErrorAction SilentlyContinue | Select-Object Identity, User, AccessRights, SharingPermissionFlags
}

The above is a simplified example, ideally you'd add some error handling to this script and export the results to a file rather than the console

If you wanted to query all mailboxes and not use a CSV file as the input, then you could change the $mailboxes variable to:

$mailboxes = Get-Mailbox -ResultSize Unlimited