Here's how to do it:
1) Open KNotes.
2) Right-click on the knotes icon in KDE's "system tray" - Choose "KNotes einrichten" (Knotes settings?)
3) On the left, choose "Actions" (Blue KDE wheel)
4) Replace the "KMail" calling string with
Note:The spaces before and after %t and %f are important, because otherwise, KNotes' parser won't see them.mozilla-thunderbird -compose subject= %t ,body= %f