You will need the following to achieve that:
- Gmail Account
- PayPal Account
- at least basic Zapier account (you need multi steps)
Look at this tutorial first from arpReach blog: click here.
You will need this search on Gmail:
from:(firstname.lastname@example.org) subject:("You received a payment") "for [name of your product]"
For the next steps (for selecting the list) and add the contact follow the arpReach tutorial from step 3.