Plain text format is one that all e-mail programs understand, however:
1. it doesn't support bold, italic, colored fonts, or other text formatting.
2. It also doesn't support pictures displayed directly in the message body (although you can include them as attachments).
Outlook Rich Text Format (RTF) is a Microsoft format that only the following e-mail programs understand: Microsoft Exchange Client versions 5.0 and 4.0, Outlook 2002, Outlook 2000, Outlook 98, and Outlook 97.
RTF format is generally used by businesses:
You can use RTF when sending messages within a company that uses Microsoft Exchange Server; however, it's recommended that you use HTML. RTF supports text formatting, including bullets, alignment, and linked <mk:@MSITStore:C:\Program Files\Microsoft Office\Office10\1033\olmai n10.chm::/html/olconAboutOutlookMessageFormats.htm#> objects. Outlook automatically creates meeting and task requests and messages with voting buttons in RTF format, regardless of the default format you have set.
Jean