alt Hacker NewsIMAP is a horrifically insufficient protocol. Literally every mail provider just implements their own custom JSON protocol to use with their own proprietary apps. Fastmail created JMAP which was meant to be an open source standard but so far only Fastmail uses it so it's just another provider specific protocol and client.
I do think 2027 might be the year that JMAP finally gets wider adoption! Between Thunderbird using Stalwart for their hosted product, and the fact that the new agentic tools are very good at writing JMAP integrations, I expect plenty of much better JMAP tooling.
I'm also close to a much more releasable version of the proxy which was first written back in 2014: https://github.com/jmapio/jmap-perl/ -- which can wrap existing IMAP/CalDAV/CardDAV/Submission infrastructure so you can access it via JMAP.