For the moment, the list of Trac plugins installed can’t be changed. However, in future you will be able to pick and choose which plugins go into your Trac install. Additionally, you will be able to recommend new plugins to be support and as they’re added in you will be able to use them.

If its something urgent, I can do it as a one-off for your project, but it might take a while, and won’t be a standard install.

I haven’t come past that before, but if I look at http://trac.edgewall.org/wiki/TracNotification it seems the behaviour that you want is the setting called smtp_always_cc ?