I just installed your plugin and the system is doing a couple things:
a) When I create a double-opt-in message or an autoresponder message, the "save" button wipes out not only the message, but the box that was used to create it.
b) I tried adding an email address to the mailing list, but the list remained empty.
I returned to the settings screen, and the sender email box is empty, my notification choice is not checked, and the double-opt-in message box is still gone.
Does this plugin not work with 3.7.1?