[WorldMaker]

The big pitch for JMAP is for a modern web-tech-only approach to email/calendar/"groupware" servers. One reason to do that would be to make it easier to also build email/calendar/"groupware" clients entirely out of modern web-tech. Today most "web email clients" are bespoke to specific stacks/email servers. A dream of JMAP is that with the right CORS policy a single web client could interact with multiple JMAP servers, using only fetch/XHR.

The modernization efforts of JMAP are interesting, too. Most of the old protocols are a mess of bespoke plaintext formats full of quirks evolved over decades in a giant mess of different software. Even the stuff that was already web tech like WebDAV and its extensions CalDAV and CardDAV were full of quirks, violated some REST "rules", and originally intended for a different purpose (file shares/FTP replacement). JMAP is much closer to "plain REST" than WebDAV's complex HTTP protocol extensions/changes.