DKIM Signature Failing - DNS record lookup is incorrect

Question

I am running Ubuntu 12.04 on a Linode with Postfix and opendkim.

My DKIM signature is validating/passing when I test at http://www.brandonchecketts.com/emailtest.php but it is failing when I test with [email protected].

The problem is related to looking up the DNS record correctly. The elandsys test is looking up the DNS record incorrectly. I assume this is a problem with my configuration and I would like to know how to fix it.

The test at brandonchecketts.com looks up the DNS record correctly using:
Building DNS Query for list._domainkey.my_example.common

The test at elandsys looks up the record incorrectly using:
no DNS record for _domainkey.list.my_example.com

My opendkim SigningTable includes this entry:
*@list.my_example.com list._domainkey.my_example.common

My opendkim KeyTable includes this entry:
list._domainkey.my_example.com list.my_example.com:list:/etc/opendkim/list.private

I'll post the two tests in detail below. The first one shows DKIM validating correctly. The second shows the problem as reported by elandsys.

brandonchecketts.com DKIM Signature - PASS

Message contains this DKIM Signature:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=my_example.com;
    s=list; t=1336xx239;
    bh=cS8QYxxxsPwl7ZB=;
    h=Subject:From:To:Date:List-Id;
    b=VYpXM...rBHWA+


Signature Information:
v= Version:         1
a= Algorithm:       rsa-sha256
c= Method:          relaxed/simple
d= Domain:          my_example.com
s= Selector:        list
q= Protocol:        
bh=                 aS8QYiOQ..sPwl8ZE+
h= Signed Headers:  Subject:From:To:Date:List-Id
b= Data:            VYpXM...rBHWA+
Public Key DNS Lookup

Building DNS Query for list._domainkey.my_example.com
Retrieved this publickey from DNS: v=DKIM1;k=rsa; t=y;  p=TIGfMA..AQAC
Validating Signature

result = pass

elandsys DKIM Signature - FAIL

Date: Sat, 11 May 2012 11:45:05 -0700 (PDT)
Message-Id: <[email protected]>
From: [email protected]
To: [email protected]_example.com
Subject: Auto-response from dk.elandsys.com
Sender: [email protected]
Auto-Submitted: auto-replied


This is an automatic response.  Replies to this message will not generate
an automatic response.
Do not reply to this message except for reporting a problem.

The results are as follows:

DKIM Signature validation: DKIM-Signature could not be verified
DomainKeys Signature validation: not available
DomainKeys Policy: no DNS record for _domainkey.list.my_example.com
DKIM Author Domain Signing Practices: no DNS record for _adsp._domainkey.list.my_example.com

ADSP is not required for DKIM signature validation.

Note: The authentication results are not available as there was no signature header or the signature could not be verified

Here's some version info:

opendkim -V
opendkim: OpenDKIM Filter v2.5.2
        Compiled with OpenSSL 1.0.1 14 Mar 2012
        SMFI_VERSION 0x1000001
        libmilter version 1.0.1
        Supported signing algorithms:
                rsa-sha1
                rsa-sha256
        Supported canonicalization algorithms:
                relaxed
                simple
        Active code options:
                USE_DB
                USE_LUA
                USE_UNBOUND
                _FFR_REPLACE_RULES
                _FFR_SELECTOR_HEADER
                _FFR_STATS
        libopendkim 2.5.2:

dpkg -s postfix
Package: postfix
Status: install ok installed
Priority: extra
Section: mail
Installed-Size: 3353
Maintainer: LaMont Jones <[email protected]>
Architecture: amd64
Version: 2.9.1-4
Replaces: mail-transport-agent
Provides: default-mta, mail-transport-agent
Depends: libc6 (>= 2.14), libdb5.1, libsasl2-2, libsqlite3-0 (>= 3.5.9), libssl1.0.0 (>= 1.0.0), debconf (>= 0.5) | debconf-2.0, netbase, adduser (>= 3.48), dpkg (>= 1.8.3), lsb-base (>= 3.0-6), ssl-cert, cpio
Recommends: python
Suggests: procmail, postfix-mysql, postfix-pgsql, postfix-ldap, postfix-pcre, sasl2-bin, libsasl2-modules, dovecot-common, resolvconf, postfix-cdb, mail-reader, ufw
Conflicts: libnss-db (<< 2.2-3), mail-transport-agent, smail
Conffiles:
 /etc/init.d/postfix 4af3a2532cddca3e6d0bc5f7b4fc2f75
 /etc/insserv.conf.d/postfix 7fe2d086ff4822fc9fe13adab1090dce
 /etc/ppp/ip-up.d/postfix fccc53fc4eeeab46941ebcc95a71e766
 /etc/ppp/ip-down.d/postfix 52275dc23864f3bfca412c7558e28fe6
 /etc/network/if-up.d/postfix fccc53fc4eeeab46941ebcc95a71e766
 /etc/network/if-down.d/postfix 52275dc23864f3bfca412c7558e28fe6
 /etc/postfix/postfix-script 0d01860b2f0778cf41951c801f538b30
 /etc/postfix/post-install 4e9b37279a95246a5fe68afdbbbfd035
 /etc/postfix/postfix-files ad34dcc8c31d057f6f20268b0aa16f29
 /etc/rsyslog.d/postfix.conf d8a09827fff2a22311e4dd4a83e95c83
 /etc/ufw/applications.d/postfix 5c7e746dc9255e750b8f50460de11a32
 /etc/resolvconf/update-libc.d/postfix cfdfa512e14e80ab89cac7cc44b3a521
Description: High-performance mail transport agent
 Postfix is Wietse Venema's mail transport agent that started life as an
 alternative to the widely-used Sendmail program.  Postfix attempts to
 be fast, easy to administer, and secure, while at the same time being
 sendmail compatible enough to not upset existing users. Thus, the outside
 has a sendmail-ish flavor, but the inside is completely different.

Solution

I believe [email protected] is broken. That appears to be the problem. Unless it gets fixed, just don't use it. Use the others.

Our DKIM is passing:

• Brandon Checketts Email Validator - http://www.brandonchecketts.com/emailtest.php
• Send a signed email to: [email protected]
• Send a signed email to: [email protected]

The only test it is failing is:

• Send a signed email to: [email protected]