Update RemoveMailboxpermission.md

Added changes made to mailusers

Author: ChandraKavya

exchange/exchange-ps/exchange/mailboxes/Remove-MailboxPermission.md

@@ -17,6 +17,8 @@ This cmdlet is available in on-premises Exchange and in the cloud-based service.
 
 Use the Remove-MailboxPermission cmdlet to remove permissions from a user's mailbox.
 
+Use the Remove-MailboxPermission cmdlet to remove permissions from a mailuser in Exchange Server 2016, Exchange Server 2019 and Exchaneg Online.
+
 For information about the parameter sets in the Syntax section below, see [Exchange cmdlet syntax](https://docs.microsoft.com/powershell/exchange/exchange-server/exchange-cmdlet-syntax).
 
 ## SYNTAX