mz.ru is broken.
maxmail.co.uk is horribly broken. maxmail.co.uk should win the "Broken
of the year" award.
Everything is working the way it should be working.
I didn't state that these domains' DNSes are not broken, I just said that
courier reports these existent domains as nonexistent. The fact that some
domain have broken DNS records could not automatically be treated as the
reason for bouncing all mail from that domain.
It most certainly is. That's the whole purpose of the CHECKDNS option: to
bounce mail from undeliverable domains. None of those domains are