ARC: A Standard We’re Proud to Support

The Internet works best when companies come together to work collaboratively on open standards that benefit us all — and because our business is built on one of those standards, DMARC, Valimail believes strongly in the importance of giving back. That’s why Valimail has been a committed contributor to open-source and industry standards bodies since we were founded in 2015.

Case in point: We’ve worked closely with industry leaders to draft the proposed standard for Authenticated Relay Chain (ARC), for which I’m proud to be listed as a co-editor. We've also contributed extensively by shipping code. We've developed an ARC test suite, and used that to drive development and further contributions to core ARC libraries like OpenARC, dkimpy, and Mail::DKIM.

So we’re gratified when we see other companies joining the bandwagon and supporting ARC. Two years ago, there was a strong belief that ARC was what the ecosystem needed to resolve existing shortcomings, but the standards and software needed to implement it were sorely lacking. Since then, it has progressed to the point where most of the major email service providers are conducting tests and seriously considering rolling it out. We’re proud of the work we’ve done to help bring it to this point, and we’re happy to see more and more companies joining the ARC effort.

ARC solves one of the last remaining obstacles to widespread DMARC adoption: The difficulty that email authentication has when mail is sent via an intermediary, either through an alias (like a college alumni forwarding address) or through a mailing list (like the Mailman discussion lists used by many internet standards bodies for coordination and collaboration). Although this problem affects a very small percentage of overall email volume, it can cause DMARC authentication to fail when it shouldn’t — and that’s a problem.

ARC addresses this by letting intermediaries attach and sign authentication information they receive, essentially creating a chain of trusted signatures. Receivers can validate every step of the chain, all the way back to the originating server, and they can leverage the information intermediaries added to make final delivery decisions they otherwise would have been unable to make. This gives email services a flexible, robust way to handle email authentication even when messages pass through multiple forwarders.

Like DMARC, ARC will only succeed if it broadly adopted and widely supported. DMARC now enjoys the support of nearly 80 percent of all email inboxes worldwide, and the number of domains deploying DMARC records has tripled in the past year. We look forward to the day when ARC is just as ubiquitous!

Seth is the director of industry initiatives for Valimail.