It appears that Bryan Fields via NANOG <nanog@lists.nanog.org> said:
ARC/RFC8617 was considered, but right now other than google, it appears to be not widely used. If this was widely supported, it appears to be a good solution.
ARC turned out to be a failure since it depends on knowing that the system sending you mail with ARC seals is trustworthy, and that doesn't scale. The IETF is currently working on a follow-on to DKIM tentatively named DKIM2 that is intended among other things to do what ARC was supposed to do in a more scalable and verifiable way. I hope by the end of the year we can have trial code for mailing list software to see how it works. The large mail systems are all involved in this and are as eager as anyone for it to succeed. R's, John