SunMailer generates the content of the newsletter as XML and then uses XSL to transform the XML into HTML or text. SunMailer comes in with a built-in HTML and text design for the newsletter. To redesign the newsletter, do not modify the XSL files for the built-in designs. Instead, create a new XSL file for the new design. The XSL files for the built-in designs (html-default.xsl and text-default.xsl) will provide a good reference. Under the Site building page for Sunmailer, there is a Designs tab used to upload the XSL file for a new design. Once created, a design can then be used for any newsletter. The XML for the newsletter will grab information from three sources: