I tried using the JMAP bridge to develop a modern client as you mention, but there were huge problems with it. It appears to be abandoned, and Fastmail’s demo i

I tried using the JMAP bridge to develop a modern client as you mention, but there were huge problems with it. It appears to be abandoned, and Fastmail’s demo install of it is entirely broken too. I ended up using the underlying lib that this project uses (also by andris9) and have had basically no problems whatsoever, it was a night and day difference.