Wietse Venema: > Wietse Venema: > > kawakami: > > > And this problem occurs NOT always, only in following situatision, > > > > > > > 2, A message was sent on IPv4, but resuted 451 error. > > > > 3, A message was sent on IPv6, but resuted 451 error. > > > > After a 4xx error, the SAME Postfix SMTP client process may > > IMMEDIATELY try to make the SAME delivery to a different MX host. > > If this is new, please read the SMTP protocol spec, RFC 5321. > > And as always, DO SHOW LOGS.
And configuration, as requested in http://www.postfix.org/DEBUG_README.html#mail Wietse
