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There are some emails with an X-DKIM header (next to DKIM-Signature) like this:

X-DKIM: Sendmail DKIM Filter v2.8.2 DOMAIN SOMEVALUE

However I am unable to find decent documentation for it. What is it for? Is it necessary?

Jasper
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1 Answers1

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My guess, this header just some meta-information about DKIM processing milter, especially the deprecated dkim-milter.

X-DKIM: Sendmail DKIM Filter v2.8.2 DOMAIN SOMEVALUE

  • DOMAIN: Hostname in FQDN format
  • SOMEVALUE: queue ID when this message processed by sendmail

For example, X-DKIM header from this question.

Received              : from localhost ([my_mailclient_ipaddress]) (authenticated bits=0) 
                        by my_smtpserver_hostname (8.14.2/8.14.2) 
                        with ESMTP id n9SCX6ml017820 for ; 
                        Wed, 28 Oct 2009 08:33:08 -0400
X-DKIM                : Sendmail DKIM Filter v2.5.1
                        my_smtpserver_hostname n9SCX6ml017820
DKIM-Signature        : v=1; a=rsa-sha256; c=simple/simple; d=mydomain[dot]com; s=mydomain;
                        t=1256733190; bh=oBeBoCqUcTrV/4cgaMK58OrPkchqCMzB2Vax aRRph6g=;
                        h=From:To:Subject:Date:Content-Type:MIME-Version;
                        b=faLHQ jAakBDkxbz8xhGmfi2ZfBHXUBFOWTZs9BAfaksB8lJghho6YmUPKIY5oMJMsCkh/QLQ 8RXD8dUPf04X6A==
Community
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masegaloeh
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    It is funny that it is so hard to find some documentation considering this. Until I hear sth different, I will just ignore the header. I'll keep this open a little longer, but thanks! Also I would have really liked to hear the reasoning behind the downvotes... – Jasper Dec 17 '14 at 08:43