Enabling e-newsletter plugin on a multisite


I have a wordpress multisite installation. The e-newsletter plugin is activated on my main site. I have setup the plugin to automatically subscribe to the newsletter any user registering to my main site.

However the thing is now I'm getting registration from my other sites as well. Apart from adding those registrants manually, there isn't an option to capture those registrations automatically like it is with the main site. I tried to network activate the plugin but no avail. It's seems to only work on per site.
Adding manually is really a daunting task because wordpress doesn't sort users base on their registration date.

So my question is Can I setup E-newsletter plugin to capture user registration from other sites as well?
If it's not possible with the current version please consider adding this feature in a next update. In my view this shouldn't be a big problem as multisite users share the same database.

Thanks and have a great day!