Symptoms
By default, the Start-MailboxAssistant cmdlet is not available in the Exchange Management Shell (EMS) for Microsoft Exchange Server 2019. Currently, admins have to add the "Microsoft.Exchange.Management.Powershell.E2010" plugin to enable the cmdlet. This action bypasses Role Based Access Control (RBAC) verification.
Resolution
To fix this issue, install Cumulative Update 12 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.
