[Cialug] Postfix issue

[L. V. Lammert]

I discovered an issue recently with a Postfix server:

Received: from jsyvahmofr.pw (unknown [137.175.19.248])
        by mail2.omnitec.net (Postfix) with ESMTP id 6579991E85

This box is *accepting* emails from unknown hosts, .. yet main.cf includes
the required reject_invalid_hostname!

smtpd_recipient_restrictions = permit_mynetworks,
permit_sasl_authenticated,  reject_unauth_destination,
reject_unauth_pipelining,  reject_invalid_hostname,
reject_unknown_sender_domain,  reject_unknown_recipient_domain,
reject_non_fqdn_sender,  reject_non_fqdn_recipient,  reject_rbl_client
zen.spamhaus.org

I did not build this box, and I am reluctant to change a config that
otherwise is working properly.

Any clues as to why this box is accepting invalid hostnames?

	TIA!

	Lee