DMARC has been around for about 5 years. It's supported by many email providers and domains.
https://en.wikipedia.org/wiki/DMARC
DMARC is a policy set up by the owner of a domain to specify how failure of SPF and DKIM will be handled. I don't have a Runbox account so don't know if they support SPF, DKIM, and DMARC.
- When sending, SPF, DKIM, and DMARC must be enabled in the DNS records for the sending From domain. DKIM security signing must also be implemented by the sending server.
- When receiving, SFP, DKIM, and DMARC are supported by the receiving server (if implemented). Some systems only support some of these standards (such as DKIM only).
- Conventional message automatic redirection/forwarding breaks SPF as implemented in DMARC. DKIM can also be broken during forwarding if certain portions of the message are altered. Because of this, automatic redirection is now risky and can't be guaranteed to work between all accounts. That's the price we pay for reducing spam and phishing.
Bill