"1. Click "Help▼" in the Upper Left-hand side of the Beta Mail screen.
2. Scroll down, click ► "Return to Original Mail".
3. When you reach the Confirmation window, Complete the form, then click Continue.
4. Allow the mail page to Reformat...
You will then be returned to the Previous Version of Mail.
•Should it switched to "All-New Mail" merely do this:
1.click "Options▼" at right side of mail page
2.click "Mail Options"
3.click "Switch to Classic"
4.Allow the Mail Page to Reformat to Classic Mail..."
Sursa : http://answers.yahoo.com/question/index?qid=20110411192757AAGq9SO
O zi buna! :)