I'm on Windows 7 and when I choose 'Email Photo' it opens an email with the photo as an attahcment before sending the file. I then have to manually hit 'Send.'
This Adobe help reference seems to indicate LR only sends images as attachements. What email application are you using?
http://help.adobe.com/en_US/lightroom/using/WS2bacbdf8d487e582725869a7 13414c552c0-8000.html