There isn't a way to verify it with PayPal. You can try sending an email to the email address to see if email gets bounced back to you due to there being no such email address.
However, if an email address is not associated with a PayPal account, the payment status will be "Pending" awaiting for recipient to claim payment with a "Cancel" link at your disposal, where applicable. If an email address is associated with a PayPal account, the payment will generally be marked as "Completed".
Should there is a problem, click the transaction, then click "Report a problem". Whatever you do, do not dispute as Unauthorized since no one broke into your account to make this transaction. Choose Item Not Received or Signifcantly Not As Described. Choosing the appropriate dispute type makes or breaks your dispute/claim.