If you are using the Approve Each Message option, then you can list additional email addresses to receive your message, prior to the message being approved.

This allows you to see how your email looks at various ISP's and in different email readers, prior to approving your message for your regular subscribers.

Unless you also add these email addresses to your list, they will not receive the same message when you Approve the message.

In order to preview your message, you'll need to ensure that the "Approve Each Message" option in your mail-list account is on. Please refer to this lesson to learn how to turn it on:

How Do I Approve or Reject a Message Before It Goes Out to the Subscribers