[robn_fastmail]

IMAP works, but not particularly well for a lot of modern tasks. Its highly stateful, requires a fair amount of knowledge on the part of the client to make things work correctly, and too many extensions are optional, requiring a lot of fallbacks for when functions are missing. Implementing a client or a server well is difficult.

JMAP isn't the be-all and end-all of mail protocols, but it goes some way to address some of the problems in IMAP. We're using it in production right now at FastMail so we already know its pretty good as a low-latency, stateless protocol.

As for the IETF (and standards bodies in general), they're useful in their place, but they're also a slow-moving beast and thev're published a great many "standards" that have either never been implemented or are just rubbish.

But there's nobody forcing you to implement it. Its there, its documented, and we're encouraging others to get involved to make it work. If others get on board then we'll see improvements everywhere. If not, then FastMail will continue to use it and get the advantages that come from it.