Check the email headers to find out the mail server that sent it. It should look like this if it's from paypal:
The bolded text is the sending mail server. Obviously yours won't say paypal.com but check a few of them and see if they are from the same server. If they are then it may be worth your while to email owner of the domain and report the spam. If it says "blahblah.blah.ISP.COM" then there usually is a corresponding email address like
[email protected] that you can forward the email to.
PM me if you need help.