This command will show you who has full access to a mailbox – explicitly added permissions only – using the EMS. You could of course do it one by one in the EMC if you like pain.
Get-Mailbox -Server “mailboxserver” | Get-MailboxPermission | where { ($_.AccessRights -eq “FullAccess”) -and ($_.IsInherited -eq $false) -and -not ($_.User -like “NT AUTHORITY\SELF”) } | fl
