Dear ComposeIT users, our attention was just brought to the fact that the installer that ships with ComposeIT 1.4 is broken. Thanks Dmitriy! For now, please quit Mail.app, and manually copy ComposeIT.mailbundle to ~/Library/Mail/Bundles. ComposeIT 1.4 itself will work just fine. We are scrambling to fix the installer to bring back the streamlined install experience. Sorry for the slip folks!