Airmail is one of the slicker and more dependable email clients available on Macs. Easily manage multiple email accounts from one interface. The message organization capabilities are impressive and easy to use.
The good thing about the Airmail setup is that it is fairly easy and copying a whole batch of email folders between your Macs is straight forward. You simply need to go to the Show Airmail Data and everything is synced. The interface is simple but pretty. You will find the icons for all your accounts on the left hand pane. For some email accounts, the Airmail application drags in your picture to make it the profile icon. There have been reports this feature is a bit buggy. Thankfully, you can always change icons manually.
Airmail picks up accounts from Google, iCloud and even Gravatar to make contacts icons. The spam filtering is also very clear but you have to right click and mark the emails as spam. You can switch between accounts by clicking their respective icons.
This is a simple and appealing email client that works flawlessly with Gmail.