The plain text version of your message is created automatically from the HTML version. It is always automatically embedded so that users with email programs that cannot read HTML will still be able to read your message.
You can use plain text view to customize the plain text version.
You can optionally send in plain text only. In the Send tab, click the Send button. Click More, then check the Send plain text only checkbox.
From the dropdown, choose whether to send plain text to all contacts or only AOL.