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.
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.
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.