Fully customizable swipe actions: Set custom actions for left and right swipe or broadening the possibilities even more by distinguishing between partial and full swipe, giving the user 4 actions instead of just 2. On Mobile and if possible also in the browser client. The mail client Spark (as horrible as their privacy policy might be, but their swiping game is awesome) is the only client/app I know that has this feature implemented and it is an absolut blessing for the UX.
snowball
Fully customizable swipe actions: Set custom actions for left and right swipe or broadening the possibilities even more by distinguishing between partial and full swipe, giving the user 4 actions instead of just 2. On Mobile and if possible also in the browser client. The mail client Spark (as horrible as their privacy policy might be, but their swiping game is awesome) is the only client/app I know that has this feature implemented and it is an absolut blessing for the UX.