This blog post states:
I've emailed someone a Ranorex report with a .html extension, but he can't view it in his browser. For a report called abc.rxlog or abc.html, exactly which files need to be compressed?To share a Ranorex Report you can manually compress all files necessary for reporting and attach the corresponding package to your mail. ...require that the Ranorex Report Viewer is installed on the machine receiving the shared Report.
To overcome this requirement simply change the extension form “*.rxlog” to “*.html” in the Test Suites properties pane.