DKIM message signing comes to Google Apps

Stephen Withers
Monday, 10 January 2011 10:49

Business IT - Security

Google Apps customers can now easily add DKIM signatures to outgoing emails.

Spam volumes might have dropped last quarter, but the size of the decline is a moot point. Symantec reckons it fell by 56%, Israel-based Commtouch said 30%, and Germany-based eleven put the number at 15%. Whatever the real number is, spam is still a problem.

One way of reducing the effectiveness of spam is to provide the recipient with some assurance that messages did originate from their purported sender. It would not of itself reduce spam, but an email that wasn't from the named sender could be subjected to more rigorous filtering.

And that's the idea behind DomainKeys Identified Mail (DKIM). Derived from early work by Yahoo! and Cisco, it adds a digital signature to an email. It works at the domain level and therefore doesn't confirm the identity of the individual that sent the message, but without something like this it is trivially easy to fake an email's From header.

The public domain key is made available in the domain's DNS records so any DKIM-enabled software receiving a signed message can check its validity.  

Google has now begun offering DKIM signing in the Google Apps version of Gmail at no extra charge.

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