Google can help remove a strong incentive for criminals to steal and leak emails by rotating and publishing DKIM keys, which provide proof of an email's origin (Matthew Green/A Few Thoughts ...)

Matthew Green / A Few Thoughts on Cryptographic Engineering:
Google can help remove a strong incentive for criminals to steal and leak emails by rotating and publishing DKIM keys, which provide proof of an email's origin  —  The Internet is a dangerous place in the best of times.  Sometimes Internet engineers find ways to mitigate the worst of these threats, and sometimes they fail.