dkim-milter support has been discontinued. You should instead switch to OpenDKIM, http://www.opendkim.org.
That said, the error means you’re getting mail from someone that’s signed by a key that can’t be found in the DNS. The error is legitimate, and there’s not much you can do about it other than ignore it or filter mail from that source.
From: Admin [mailto:email@example.com]
Sent: Friday, February 17, 2012 10:09 AM
Subject: [dkim-milter-discuss] error on DKIM one inbound domain
Hello. can someone help me get this error and continuing server errors with DKIM?
The problem is that i am getting this in my OSSEC logs my the thousands from this ONE domain. Postfix, mailman. I have no other problems with DKIM ever, but for the last few weeks with this error.
Received From: www->/var/log/maillog
Rule: 1002 fired (level 2) -> "Unknown problem somewhere in the system."
Portion of the log(s):
Feb 16 20:42:47 www dkim-filter: 560704ACD3D: key retrieval failed (s=k1, d=monobestoffers.info): res_query(): `k1._domainkey.monobestoffers.info' Unknown host
IT would not bother me, except i have blocked the ip from the firewall and continue to recieve the errors and am worried about the load on the mailsystem and server.
How can I stop it and what is going on, any help would be appreciated.