from the article itself: "Finally, we know IMAP, SMTP and the DAVs aren’t going away any time soon. No protocol will succeed unless it provides an upgrade path

from the article itself: "Finally, we know IMAP, SMTP and the DAVs aren’t going away any time soon. No protocol will succeed unless it provides an upgrade path from where we are now, and a compelling reason to switch. We will provide a proxy which can talk to existing servers and present them over JMAP."