I found some contacts like https://civicrm.wikimedia.org/civicrm/contact/view?reset=1&cid=66781861 who have clearly created a recurring paypal donation using a link emailed out with a check sum and hash. As part of our paypal processing we have either not received or not kept the email due to the paypal-recurring behaviour and have deemed them to be a new contact. However, this has resulted in us creating new contacts with no email - ie we lost the email

The list of referral donors is here https://civicrm.wikimedia.org/civicrm/referrals and the ones I'm looking at are the ones with no email for the new donor. I was thinking DR might want to dedupe some of them but we should probably dig into these no email ones first