On Thu, Oct 10, 2013 at 12:47:34AM +0200, Dominik George wrote:
> Most tools, mainly libc's resolver, seem to ignore the Additional
> section and resolve relevant names on their owns, explicitly asking for
> the RR types they are itnerested in, and that's what seems to be
> appropriate. Postfix, however, seems to rely on the Additional section
> (if it has at least one RR for the MX host?), missing out on any records
> that might be there but not cached by the uplink DNS server.
Postfix does not look at additional records. However a local DNS
cache on the machine running Postfix may well cache additional
records from an upstream resolver, and if /etc/resolv.conf points
at 127.0.0.1 (or perhaps its twin in the Postfix chroot jail), then
Postfix may get those results in the answer section when it asks
for the A records of MX hosts.
> We do not quite see an situation where this might break badly, because
> normally one MX result is to be considered as good as any other, but I
> still wanted to ask whether this behaviour is intentional and the
> limitations are known.
This behaviour is not intentional, it is fictional.
--
Viktor.
