The Mail app, which comes with Windows 8.1 and Windows RT 8.1, doesn't support adding email accounts that use POP (Post Office Protocol). This is the technology that allows email to be downloaded from the server to your PC. If your email account uses POP and you want to get it on your PC, here are some options:
If you want to use the Mail app and keep your current account, contact your email provider and ask if they can change your account to use IMAP (Internet Message Access Protocol) or EAS (Exchange ActiveSync). This change is especially useful if you want to get to your email in multiple ways (phone, personal PC, work PC, etc.), as those protocols do better than POP at keeping track of new, unread, and deleted messages and automatically saving your messages. Some providers might charge extra to switch, so make sure you check before switching.
As of January 30, 2013, Google stopped supporting new EAS (Exchange ActiveSync) connections in some scenarios. For more info, see How to sync Google services with Windows.
You can send and receive email from POP accounts using Outlook which is free as part of Windows RT 8.1.
You can use an Outlook.com account to send and receive email from another account(even one that uses POP). Then, add your Outlook.com account to the Mail app to read and send email from your POP account.
Use your email account provider’s website to get to your messages. For example, if your email account is from Contoso, go to www.contoso.com and sign in.
Look for an app in the Windows Store that supports adding email accounts that use POP.
If you want to use the Mail app and are willing to switch to a new email account, you can stop using your previous account and start using a web-based email account like Outlook.com, or Yahoo!. If messages from your original account are saved on your PC and you want to get to them in the new account, you can sign up for an Outlook.com account and then use the Mail Migration add-on to add them. Once you’ve moved to the new web-based account, you can add that account to the Mail app.