How does Membership plugin know that a paypal payment went through?

I would like to install the Membership plugin – but the newest version 3.0RC2 apparently needs WordPress 3.3.2 – and I am not sure I want to spent time and effort for this upgrade on a couple of sites running with the same 3.2.1 install.

So here my question:

How does the Membership plugin “know” when Paypal payments are actually successful? We have Single Payments as well as Recurring Payments (monthly).

In other software handling Paypal payments I usually have to adjust an IPN (Instant Payment Notification) URL which paypal will call when a payment is successful (or fails or …:wink:. Then the program at the IPN URL will adjust the database used for storing the sucess (or failure) of payments.

In the (very extensive made) handbook for the Membership Plugin I cannot find that I can provide such an IPN URL.

Did I not find it? Or does the plugin use another method (which I may not know yet)?

Thanks for any hints on this topic …