I have another verified email address associated to my paypal account, in the form me@santaclaus.com

A customer transferred cash to me@santaClaus.com (one uppercase letter) Got the email notification, but after logging in PayPal says This email address is already linked to a PayPal account. Please log in to your PayPal account with this email address to receive the payment.

Talked to support 3 times, they simply don't check it, say it's a spoof email. Just needed to vent. So sad there aren't international alternatives in wider use.