On Arrival tests 5.2.1 or 5.7.1 - ORF Forums

@jhoff: You should use 5.7.1, but it does not really make any difference in practice. 5.7.1 means "Delivery not authorized, message refused: The sender is not authorized to send to the destination. This can be the result of per-host or per-recipient filtering. This memo does not discuss the merits of any such filtering, but provides a mechanism to report such.". In contrast, 5.2.1 means "The mailbox exists, but is not accepting messages. This may be a permanent error if the mailbox will never be re-enabled or a transient error if the mailbox is only temporarily disabled.".

You probably have 5.2.1 currently configured, because your ORF configuration goes back a rather long way. We have changed the default ESMTP code to 5.7.1 in ORF 2.0, because it is better suited for the On Arrival filtering point.