Moving from Posterous

Hi guys, I need a bit of help. I am shifting my blogs from Posterous to WP. What I loved about Posterous is the ability to manage members, I would enter them, they would recieve an email invite to subscribe and then get email updates.
Is there a WP plug-in or any other way to do the same on WP? Or do I need to keep Posterous going as well to get the same ability to manage members (subscribers).
PLEASE Help ??