+1 for Spark. I know there are other clients that have snooze and ‘send later’ functions, but I’ve been using Spark for a couple of years and haven’t really had any complaints.
This is the main thing that keeps me on Apple Mail. In any kind of work context it's absolutely required for me, and the other alternative mail clients mostly concentrate on being pretty, unfortunately.
https://www.reddit.com/r/privacy/comments/5grsan/do_not_use_...