Set-executionpolicy unrestricted
$LiveCred = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred -Authentication Basic -AllowRedirection
Import-PSSession $Session -allowclobber
Connect-MsolService -Credential $LiveCred
$Identity = "joe.bloggs@demo.org.uk:\Calendar"
#Remove-MailboxFolderPermission -Identity $Identity -User "A Bloke"
#Add-MailboxFolderPermission -Identity $Identity -User steve.bloggs@demo.org.uk -AccessRights Editor
Set-MailboxFolderPermission -Identity $Identity -User "Andrew Bloggs" -AccessRights Reviewer
Get-MailboxFolderPermission -Identity $Identity