To set up a Gmail account in Mail as POP3:
- Fill in your Name, E-mail Address, and Password.
- Hold down the "Option" key.
- The "Create" button will change to "Continue", click it.
- Set your incoming mail server as pop.gmail.com.
- Hold down the "Option" key again and press "Continue".
- Complete the rest of the steps in the account creation wizard.
Occasionally, you may notice that the incoming server port is still set to 993 (which is the IMAP server port). If this happens to you, go into Mail's Preferences and change the port to 995 for your Gmail account.
Hope that helps, have a great day!