Not receiving new mail: email account is offline in Mac Mail app

Once in a while, your Mail.app (sometimes referred to as "Apple Mail" or "Mac Mail"), stops receiving new mail. You may be able to verify that you are getting new mail via webmail, another email client or computer, or even via a mobile phone. When this happens, the fix is extraordinarily easy!

Here's how: From inside the Mail.app, click the Mailbox menu:

• Choose "take all accounts offline", and wait 10 seconds.
• Choose "take all accounts online".

You should begin seeing your new mail flow into your inbox.