I have used several Email Apps on my Mac. From recent memory I have used Spark, Airmail, Blue Mail, HEY and Postbox. I receive a lot of Email, so my Email workflow is important to me. This article lists what they consider to be the best Email Apps for the Mac. It is pretty informative. Having used several of the Apps in their list I can vouch for the accuracy of their evaluations. By the way, I have switched my Email workflow to HEY which is a totally different way of doing Email.