Though I have no complaints about the way they went about implementing it (open standards hooray!), as a mail client author and someone with lots of experience with mail in general - I'm NACK to JMAP. I think that it comes with some questionable design decisions (HTTP? JSON?) which on their face I imagine look fine to the typical HNer, but in many ways is a regression from IMAP. I would prefer to see the limitations of IMAP addressed with a few carefully written extensions to the spec - which is already extensible and has a thriving set of useful extensions in the wild.
By no means is IMAP a particularly good protocol, but it is extremely broadly supported and designed more with email in mind than JMAP appears to be, which seems to focus more on bringing shiny web tech to email regardless of its utility in such a context. It's also one of many closely interlinked mail-related specifications, and JMAP fails to integrate well with many related specs imo.
By no means is IMAP a particularly good protocol, but it is extremely broadly supported and designed more with email in mind than JMAP appears to be, which seems to focus more on bringing shiny web tech to email regardless of its utility in such a context. It's also one of many closely interlinked mail-related specifications, and JMAP fails to integrate well with many related specs imo.