Postfix - Hostname Verification Failed Of course I tried Google - that failed miserably. As with your first link most people seam to want to disable the message rather than the actual cause!
Jun
21
comment
Postfix - Hostname Verification Failed Those options aren't active on the server, if you issue "postconf | grep client" the following results are shown:-
smtpd_client_restrictions =
unknown_client_reject_code = 450