If you send a test email from the ‘Editor’ preview page, the body of the email will appear as it will to your contacts. However, the formatting may differ in some of your contacts’ email clients.
Also, test emails include a additional item in the the standard footer indicating it is a Test Email. All special links (subscribe, optin, survey, manage subscription) would run in test mode. Every email that you send to a contact list will have a footer added that contains the CAN-SPAM compliance information such as your business address and the contact for your account.
NOTE: It is a good idea to send multiple test copies to different email clients (such as gmail, hotmail, msn, aol, etc.) This allows you to decrease layout inconsistencies.