Of course I have to ask if you've looked at JMAP ( http://jmap.io/spec.html ). More because we're getting close to finishing the spec, and feedback from someone who's build a client recently about whether the spec suits their needs would be valuable!
Hi! I really like the initiative of JMAP, however I haven't been able to look into it properly - I can give you a better answer once I've done that, my email is in my profile
I'll be in Munich in June for M3AAWG and then popping over to Paris to meet the Linagora team and chat with them about their JMAP work - don't think I can come up with an excuse to visit Sweden this trip sadly :(
My next trip after that is Montreal in July for IETF102. Hopefully we'll be finalising core and mail specs at that conference, hence the interest in getting feedback now! Easier to fix spec issues before publishing.
I've done a bunch of implementation on two different servers, so I'm comfortable with that half, but we only really have one client implementation in-house (hence wanting to chat to Linagora about theirs!)