On 2016.06.01. 17:12, Bill Cole wrote:
As Wietse has already explained, that is NOT what that setting does. "No response" as used in the documentation is different from a non-error response with no answer records, a response that the domain does not exist, or a server failure response. "No response" is what you get when a DNS server is unavailable or takes so long to answer that your resolver times out. There is no need to explicitly set ignore_mx_lookup_error to "no" because that is the default, complying with the RFC5321 delivery specification. Setting it to "yes" can result in fast permanent failure of delivery instead of a transient failure that might resolve in a short time. Yes. This is how email routing has been done since the widespread deployment of DNS to replace distribution of the global HOSTS.TXT file, about 30 years ago. A description of how the MX RRTYPE and A fallback came to exist with the relevant RFC references is at https://en.wikipedia.org/wiki/MX_record#History_of_fallback_to_address_record I know of no way to do that in Postfix, short of patching the source code in a way which would be incompatible with how Internet email has operated for the past 30 years. Fallback to A records in the absence of any MX records is the only way to get email to addresses in some domains. There is not (and never has been) any standard requiring a MX record for any domain name that can accept email. Such a requirement would needlessly bloat some DNS zones and increase DNS traffic volume because a "no answer" reply to an initial MX query is smaller than a reply with an answer record of the same name as the one being queried.
OK, that's clear now. Thank You for explanation! -- KSB
