Windows 8 comes with a bundle of Start screen apps and some are quite good. The Mail app is OK as far as it goes, but the problem is that it is quite limited. It is fine with Hotmail and Gmail, and IMAP in general, but POP email is not supported. If you try to add a POP email account it just reports that POP3 is not supported. However, there is a way around this.
IMAP and POP are different ways of accessing email. IMAP (Internet Message Access Protocol) is used to access email stored on a remote server and it is fine for Outlook.com (it used to be called Hotmail) and Google Mail where the services store your email online. POP (Post Office Protocol) is used by email clients that download emails and store them locally, such as on the computer's disk drive.
POP, or POP3, email is more common and your ISP or workplace may provide you with an email account. When you try to add it to the Start screen Mail app, it just says sorry, it's not supported.
A useful feature of Outlook.com (formerly Hotmail) is that you can add other email accounts. Another account, even a POP3 one, can be added to Outlook.com and it fetches the email messages at regular intervals and stores them in a separate folder. It turns out that when you add the Outlook.com email account to the Mail app, it also adds those other email accounts. Mail is just a mirror image of what's on Outlook.com, so if Outlook.com is fetching your POP3 email then it appears in Mail too.
Go to outlook.com in your web browser and log in if it doesn't do so automatically. Click the gear icon at the top right and select More email settings. Click Your email accounts under Managing your account. Click Add a send-and-receive account. Enter the email address of the POP3 account and the password. Sometimes Outlook.com can figure out the settings by itself, but sometimes you need to click the Advanced options link and add the server address. You will need to know this and it will be something like mail.somewhere.com. The port number may ve required too and 110 is commonly used for email. If you aren't sure you should consult the help pages from your ISP or company, or check the settings if you have previously set up an email program.
That's all there is to it. Once it is set up in Outlook.com, it will appear in the Mail app. Just run it and it will sync.