Adding JMAP would be a definite +1 for me. I use fastmail and their web interface is good and mobile app is better. I use Thunderbird on my Mac because I need

Adding JMAP would be a definite +1 for me. I use fastmail and their web interface is good and mobile app is better. I use Thunderbird on my Mac because I need things like smart signatures that are dependent on my outgoing email address but I want a combined Inbox. A native app that supports JMAP and provides that sort of integration would let me migrate from Thunderbird, which while it's been awesome for the years I've used it, is showing its UI age.