Q:

Session being cleared during paypal Express checkout

I am currently developing an E-Comm site that uses Paypals express check out system. The express checkout system works fine, I send the payments amount, the user logs in to confirm the shipping details, and returns back to my page where I confirm it and the payment is completed. The main issue I am having is that I have the username (email) saved in the session. Once the user clicks checkout with paypal and confirms his/her paypal account, my session is cleared. So I cannot keep a record of who purchased what item (unless I use the users paypals email address which could be different from the one the user used on my site). 
So my question is, is there any way that I can preserve the session state throughout this confirmation action? Or is there another way to keep the users information? is this a documented problem (I have not seen it anywhere)?
If any more detail is required let me know.
Thanks for your time.

A:

No, once the user leaves your domain the session will terminate. 
Instead you can store the email address in a table before user leaves your site and pass the ID of the inserted record to paypal. As this ID is a custom field it will be returned in the call back url once the user completes the payment. You can get the ID from URL and retrieve the corresponding email from database. 

