You can use an Outlook.com or Hotmail account - any Microsoft online email that creates a Microsoft account - as an email Tile in the Start screen. First of all, use the Microsoft account from that Outlook.com or Hotmail account as the Microsoft account you use to login to the Surface. Set up your 3rd party emails (Google, Yahoo, etc.) in the Outlook.com or Hotmail email account (including POP accounts, something the Mail app can't do).
From the Start screen login in to that Outlook.com or Hotmail account in Internet Explorer 10 UI, you can pin that webpage to the Start screen as a Tile by selecting the push pin symbol at the bottom right hand side (the Tile will say Outlook or Hotmail), if you save it to Favorites you can then drag it out of IE10 Favorites in the Desktop which creates a shortcut to it there (the Shortcut will say Outlook or Hotmail and your email user name).
To be on the safe side be sure to add the Outlook.com account to the Mail app, so all the Microsoft apps will sync up. The access to the People, Messaging, Calendar and SkyDrive apps are far easier within the Outlook Tile than the Mail app. Also, you can see the email address of the sender when you open an email - you can't always see that email address in the Mail app. If you are using the Outlook.com or Hotmail Tile exclusively for email, the Mail app can be unpinned from the Start screen (If desired, you can always add it back to the Start screen later).
