Hi Wietse,
On Mar/06/2022, Wietse Venema wrote: > Carles Pina i Estany: > > root@mail:~# nslookup 188.39.73.166 > > 166.73.39.XXX.in-addr.arpa name = mailcluster.zen.co.uk. > > That is sufficient to satisfy reject_unknown_reverse_client_hostname. > > But you have also configured reject_unknown_client_hostname. That > requires that mailcluster.zen.co.uk resolves to the client IP > address 188.39.73.166: > > $ host mailcluster.zen.co.uk. > mailcluster.zen.co.uk has address 212.23.6.67 > mailcluster.zen.co.uk has address 212.23.3.121 > > And that clearly does not satisfy reject_unknown_client_hostname. Just for my future reference, in: https://www.postfix.org/postconf.5.html#reject_unknown_client_hostname Reject the request when 1) (not relevant) 2) (not relevant) 3) the name->address mapping does not match the client IP address. I had missed the number 3 for reject_unknown_client_hostname Mystery solved! > You can't use reject_unknown_client_hostname for that > site, if you want to receive their email. I think that it might be possible to white list a client? Described in: https://serverfault.com/questions/202978/can-i-make-an-exception-to-reject-unknown-client-hostname I haven't tried it. Thanks Wietse (and other collaborators) for writing Postfix. As strange as it sounds: in my opinion mail is chaotic (legacy standards, etc.) and Postfix make it even fun to work with mail systems. Big thanks, cheers, -- Carles Pina i Estany https://carles.pina.cat
