Hi, I am using paypal with ipn system..

I have everything I need up until the end point.. at the end I need to send an email to the user with link registration.aspx?suc=(encode(USERNAME, PRIVATE_KEY))... two problems. 1) how do I pass the users email through to the IPN post back data. 2) how do I pass the username forward to the IPN post back call.. essentially they deal with the same issue, passing information all the way forward from original order form page and back down to the IPN post back.

I should mention that the username is not the optional email that buyer can enter (which may or may not be the same email that my user has entered in their application signup email) also the Id is not present on the seller form, I need to pass forward the userId from my application logged in user so that in the end the email can redirect to the app and decrypt with the username that I am storing in the database of users.

Thanks,