Comment 2 for bug 1277884

The desktop environment ist not recognized correctly (I use unity desktop)
I could solve this by modifiying xdg-email method detectDE()

1. sudo gedit /usr/bin/xdg-email
2. go to method detectDE() {
3. insert the follwing two lines before the if-statement
    DE=xfce
    return

this might not work for you desktop manager.
this has to be repeated in case the file is overwritten by apt-get