Modest comes stock with Diablo. It's the default email app.

Yeah, there is a User Interface with Modest.

How can I monitor the dbus activity when using this?

Well, I'm back to square one because I no longer think that restarting MCE is necessary to update any changes made with the notifications.

How can I term this argument correctly?

sudo start-stop-daemon --start --name modest


sudo start-stop-daemon --stop --name modest
works correctly. But to start it though, I need to add some kind of an additional argument that I don't understand.

-S|--start -- <argument> ... start a program and pass <arguments> to it