Great UI, you can connect to pretty much any email address (although works best with Exchange, but you don't have to host your mail on 365) and has native Windows, OSX, Android and iOS clients, all bundled in for about $6 per month. Plus if the company you work for has 365 you can usually use those licences for home too (5 device licence is standard per seat).
Plus, for that $6 a month you also get Word, Excel, Powerpoint, OneNote and 1TB of OneDrive space. I don't want to sound like a Microsoft shill, but 365 is a steal considering what you get for the cost. But it's not free.