AjaxFileUpload and file types *.MSG and/or *.EML

For some reason, since updating do version 18.1.0, the AjaxFileUpload control no longer allows uploading of .msg or .eml files. I have both listed in the Allowed File List, and am able to upload all different types of files for a long while now... but MSG and EML throw an error message in the control.  if I renamed .msg to .msg.txt its fine.. I'm baffled.