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Date: Mon, 11 Oct 2010 13:31:04 +0700
From: Eugene Grosbein <egrosbein@rdtc.ru>
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Subject: strange resolver behavour
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Hi!

FreeBSD 8.1-STABLE:

# host koin-nkz.com.
koin-nkz.com has address 62.231.164.101
Host koin-nkz.com not found: 3(NXDOMAIN)

This domain does not have MX records but NXDOMAIN seems to wrong return
code to me. Think about MTA that does look-up for MX first,
obtains NXDOMAIN and rejects mail.

tcpdump shows that after MX look-up failure resolver adds my local
domain suffix from /etc/resolv.conf's "search" clause and
goes to my local DNS server looking for MX record for
'koin-nkz.com.my.ru.' that does not exists. Hence, NXDOMAIN.

Is it a bug in our resolver?

I've tested 6.4-STABLE and 7.3-STABLE, same effect.
I've also tested 4.11-STABLE and it works correctly - no wrong
suffix addition, no NXDOMAIN.

Eugene Grosbein