[Updated for 2021] Apple Mail. I'd dare to say that the Apple Mail email app is one of the most used email apps in the world today. Outlook. If you are used to Outlook on PC or Mac, you'll be surprised how much different Outlook on iOS is when you first launch it. Spike. ... Airmail. ... Spark. ... Edison Mail. ... Twobird. ... Hey. ... Wrap-up on best email app for iPhone. ...What is the most popular email software?
Microsoft Outlook (including Outlook Express) is the most popular desktop email software followed by web-based email services from Yahoo Mail and Windows Live Hotmail.