Looks like I pasted in the data twice...
-Desktop Entry]
-Categories=Network;Email;
-Comment=GNU Emacs is an extensible, customizable text editor - and more
-Exec=/home/larsi/src/emacs/trunk/src/emacs -f message-mailto %u
-Icon=emacs
-Name=Emacs (Mail)
-MimeType=x-scheme-handler/mailto;
-NoDisplay=false
-Terminal=false
-Type=Application
-Desktop Entry]
+[Desktop Entry]
Categories=Network;Email;
Comment=GNU Emacs is an extensible, customizable text editor - and more
Exec=emacs -f message-mailto %u