I keep getting this email but I don't own or use this site so I don't know how to stop this. I removed my name and website for security reasons -
Hi <my name>,
Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) failed:
If you don't recognise this URL, you may be using a service provider that is using IPN on your behalf. Please contact your service provider with the above information. If this problem continues, IPNs may be disabled for your account.
Thank you for helping resolve this issue.