Version: (using Devel) Installed from: Compiled sources OS: Linux I think this problem not in the KDE but maybe need some cooperation mozilla's - kde's team. There is Mozilla's bug report - https://bugzilla.mozilla.org/show_bug.cgi?id=273071 As mentioned in Comment #11 (https://bugzilla.mozilla.org/show_bug.cgi?id=273071#c11) workaround doesn't work in FF 3 release.
This matter has impact to "Send link" command of FF 3 too :-(
This is not something KDE can fix. There are ways of choosing a desktop-wide default email application (xdg-email) but FireFox seems to choose not to use it.