Washington State recently passed HB 5387. This bill consists of rules for the Secretary of State and corporations.
In this bill there is an allowance for registered or certified mailing if the corporation no longer has a registered agent or after due diligence.
Another part of this bill is "service in other forms". A commercial registered agent such as CT Corp must state in its listing the forms in which it will accept service. Only those forms of service will be accepted by that commercial agent. Only commercial agents can accept by any means other than written record.