I have a small NATed network with a mail server. This machine runs sendmail with uucp transport to my ISP mailserver. Mail is transferred in batches.
My problem is with local mail.
sends mail to firstname.lastname@example.org
, the server first tries to reverse lookup my IP address and then in turn looks up domain.com and MX domain.com. The latter gets a MX record response for the ISP mail server, which I hope that this mail will not go near.
I do not run a dns server on my network, just using the dnsmasq of the firewall. As we have some dhcp machines, putting the local IP addresses in the host file is not an option.