As a user of mac mail I started to look out for other email clients because I had trouble connecting my Google accounts. Plus Apple support was of no help. I've been using Polymail from a couple of months now. Honestly, I'm pleased with it so far. It's a great tool for sales and marketing professionals. My thoughts:

Pros :

Clean & simple UI Available for both mac & IOS Provides host of productivity tools like email tracking, send later and read later Rich Contact information like Twitter bio, photo, current job, etc Email history of a customer in one place Let's you unsend emails as well. Life Saviour.

Cons:

Email sync is slow sometimes