Add .rtf, and any other file extensions that should be parsed for text, to
Tools | Options | Import | File extensions to parse text. The default is
Code:
.txt;.rtf;.doc;.docx;.xls;.xlsx;.xlt;.ppt;.pttx;.htm;.html;.eml;.nws;.msg;.mht;.xml;.pdf;.tif;.tiff;.zip