Many errors in maillog: CNAME_lookup_failed_temporarily._(#4.4.3)

Created:

2016-11-16 12:40:31 UTC

Modified:

2017-08-15 16:18:41 UTC

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Many errors in maillog: CNAME_lookup_failed_temporarily._(#4.4.3)

Applicable to:

  • Plesk

Symptoms

There are many errors in the /usr/local/psa/var/log/maillog :

 Jul 11 13:28:31 plesk qmail: 1310365711.275186 delivery 1513: deferral: CNAME\\_lookup\\_failed\\_temporarily.\\_(#4.4.3)/
Jul 11 13:29:34 plesk qmail: 1310365774.101285 delivery 1514: deferral: CNAME\\_lookup\\_failed\\_temporarily.\\_(#4.4.3)/
Jul 11 13:31:31 plesk qmail: 1310365891.566901 delivery 1517: deferral: CNAME\\_lookup\\_failed\\_temporarily.\\_(#4.4.3)/
Jul 11 13:31:36 plesk qmail: 1310365896.567026 delivery 1518: deferral: CNAME\\_lookup\\_failed\\_temporarily.\\_(#4.4.3)/
Jul 11 13:31:39 plesk qmail: 1310365899.566991 delivery 1519: deferral: CNAME\\_lookup\\_failed\\_temp

Cause

Remote DNS servers, specified in /etc/resolv.conf , cannot be queried via TCP (as Qmail tries to do):

~# host -T -tMX DOMAIN.TLD
;; Connection to 203.0.113.2#53(203.0.113.2) for example.com failed: connection refused.
;; Connection to 203.0.113.2#53(203.0.113.2) for example.com failed: connection refused.
;; connection timed out; no servers could be reached
~#
~# host -tCNAME example.com
example.com has no CNAME record
~#

203.0.113.2 denotes the remote name servers configured in /etc/resolve.conf :

~# cat /etc/resolv.conf
search plesk.hostname
nameserver 203.0.113.2
nameserver 203.0.113.3
...

Resolution

To resolve the issue, verify that all DNS servers respond to TCP DNS queries.

# host -tCNAME plesk.com 203.0.113.2
;; connection timed out; no servers could be reached
# host -tCNAME plesk.com 203.0.113.3
;; connection timed out; no servers could be reached

If they fail to as in example above, comment them out from /etc/resolv.conf file, but make sure there is least one perfectly working DNS server there.

Correct reply from DNS server looks as following:

# host -tCNAME example.com 203.0.113.2
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases:

example.com has address 1.2.3.4
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