The Apple Mail app is good, but you may want a bit more than it offers. Enter
AirMail, a well-designed app chock-full of options. This handy program lets you connect all of your cloud accounts, both email and cloud storage. The attractive unified inbox supports Apple iCloud, Microsoft Exchange, Gmail, IMAP, POP3, Google Apps, Yahoo, AOL, Outlook.com and Live.com. You can also attach files from the cloud as if they were stored locally, thanks to integrated support for CloudApp, Dropbox, Google Drive and Droplr.