Menubar icon / run in background
I love how the app integrates nicely with FastMail (there are no other apps that support all/most of the features).
It would be great if SwiftMail could run in background with a menubar icon, so that it's out of the way if I don't need/use it, and could be invoked with a global keystroke when it's needed.
For a heavy keyboard user (and a minimalist) this is a must-have for an email app, so that cmd+tabbing throught open windows is not polutted with something I don't use at the moment, but in the same time, I'd like to see notifications for incoming emails as soon as they arrive.
(I'm still puzzled why apple native Mail does not do that on mac, but does on iOS).