The email2 Toolbar for Outlook automatically converts outgoing Rich Text messages into HTML format. HTML format is a standard for communicating custom formatted information across the internet.
It is common practice for applications that support Rich Text format to convert outgoing documents to HTML format in order to maximize compatibility. As an example, Microsoft Outlook 2003 has a similar option enabled by default. The same is true for Microsoft Exchange Server.
Please note: you are still free to compose messages using the Rich Text Format, but when they are sent, they will be automatically converted to HTML format for the purposes of transportation and processing.
// Edited July 2008