Polymail is not only a beautiful email client, it is also the best. You can do everything you do on your average client but you can also track when someone clicks on your email, on a link or a file within that email.
It is great if you want to know when a client opened an email.
The client is well designed because you have a contextual card on the right side.
If you want a large delivery, a campaign feature is available. You just need to enter the right CSV and it's done.
When I think about it, scheduling emails is the best feature for my use. I always send emails at 2 or 3:00a.m but people receive them at 8:00.
I am still waiting for a PC or web version. I use a Mac but I consider switching to the PC. Polymail is, with Sketch, the only thing that makes me reluctant.