The rtf file type is mainly associated with Rich Text Format File, Text, rtffile , Word.RTF , Word.RTF.8, Jarte Word Processor, TextMaker Viewer, Zoho Viewer (Web Viewer), and with the following MIME types: application/rtf, application/x-rtf, text/rtf, text/richtext, application/msword, application/doc, application/x-soffice

This SonicWALL signature identifies HTTP downloads of Content-Type: text/richtext.