Enable RecipientValidation in Exchange Organisation

I have been troubleshooting an issue where mail was reaching our Exchange servers for non-existent recipients (it passes through a Sophos UTM first).  I discovered that there is a way of having Exchange validate the recipient and this is done using the Set-RecipientFilterConfig cmdlet, setting the RecipientValidationEnabled parameter to true:

Set-RecipientFilterConfig -RecipientValidationEnabled $true

I can now check the config using the Get-RecipientFilterConfig cmdlet: