To find the URL of an email for viewing in the browser, you will go to Step 7: Approve Email (before you actually approve it.) Look under the green "Approve" button.

Once it has already been approved and or scheduled, you can no longer get to that section without returning the email to draft and undoing all the scheduling.
To work around it:
  1. Take the base URL:
  2. Go back to the messages list
  3. Hover over any of those links for the message you want to view (copy, delete, archive, etc)
  4. You will see the message ID in the URL as it pops up on your lower screen.
  5. Enter that em_ID in the above URL, and you can recreate the URL that way.