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Growth in DKIM Signing Continues

Since my blog post last June on usage of DomainKeys Identified Mail (DKIM), there have been quite a few requests for updated DKIM signing statistics.  I’m pleased to report that deployment of DKIM signing is continuing at a steady pace, both in terms of number of messages being signed and the number of domains doing the signing.

DKIM Message Counts

As before, the above graph shows the number of signed messages received in a given week.  The gap for the month of September reflects a discontinuity in our statistics while we changed the infrastructure being used for DKIM signature verification.  For the month of February 2010, 13.4% of Cisco’s incoming email had valid DKIM signatures, not counting messages rejected by our anti-spam and anti-virus filtering.

DKIM Signing Domains

This graph again shows the number of domains from which Cisco has received valid DKIM signatures in a given week.  The jump in April 2009 represents a large email sending provider that deployed DKIM signing to a large number of its customers during that period.

As DKIM deployment grows, so does the ability to use signatures as the basis for domain-based reputation.  This is a double-edged sword:  a good reputation can enhance deliverability, but domains that send (and sign) messages that are considered undesirable by recipients can quickly tarnish that reputation and have much the opposite effect.

I remain proud of the industry’s efforts to help restore trust to email communications, and of Cisco’s participation in the development and standardization of DKIM.

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9 Comments.


  1. Sorry, there are no Graphs visible. Not in FireFox, Not in IE8 and also not in Chrome….Cisco: Thanks for the heads up, Beat. This is now changed.

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  2. Phillip Remaker

    Would be interesting to see these graphs represented as a percentage of total messages and total domains, to smooth out the holiday dips in absolute volume.I also presume the September gap was a monitoring quirk. Regardless, this is great to see the growth of DKIM! What is stopping even greater adoption?

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  3. Very interesting stuff. I had never thought about the way that certain mail providers identified junk vs. trusted content in that way. Kind of reminds me of google search rankings for sites who link to bad neighborhoods. Almost as if you are guilty by association.

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  4. Really interesting how low the number of valid DKIM emails was. 13% still is pretty low volume to me, but maybe I don’t know that much about email servers. You would like that by combined all known and verified sigs you’d get a higher number.

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  5. I employ DKIMs and first starting using them about a year a go. I too can see the charts but would be interested in percentages of total emails received using DKIM. Thanks for the stats.

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  6. This is a double-edged sword: a good reputation can enhance deliverability, but domains that send (and sign) messages that are considered undesirable by recipients can quickly tarnish that reputation and have much the opposite effect.”"This seems to leave room for sabotage. What happens when a angry client decides to start causing trouble and next thing you know customers are not getting important emails.Gmail for business does a great job of cleaning spam. I think email is restored.”

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  7. Was the DomainKeys Identified Mail data simply just disregarded in September or will you be able to retreive the data and re-post it?

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  8. I hope that DKIM really catches on as a Spam fighting tool.

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  9. Wow great read Jim. Haven’t heard anybody put their thoughts on DKIM quite that well before.

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