You might want to hide the newly created contacts from the GAL, so you can modify the New-MailContact line to be: New-MailContact $ForwardingAddress -ExternalEmailAddress $ForwardingAddress -OrganizationalUnit ‘contoso.com/Cloud’ | Set-MailContact -HiddenFromAddressListsEnabled $true

You might also want to have the mail dual-delivered (I.E. delivered to the exchange mailbox AND the cloud). This would involve modifying the Set-Mailbox line to: Set-Mailbox $mailbox -ForwardingAddress $ForwardingAddress -DeliverToMailboxAndForward:$true

Thanks again for sharing your work!