We've received reports that nations using Payflow for recurring donations are seeing duplicate transactions recorded for payments that took place in 2015 and 2016.
These duplicates are triggering autoresponse receipts to donors as well as email notifications to control panel users for donations that took place long in the past.
PayPal has renamed all transaction IDs prefaced with "B" to start with an "E" instead, so recurring donation IDs that started with the "B" in NationBuilder have been backfilling to start with an "E". Those backfilled transactions are treated as new donations since the ID is unique. This triggers an email receipt to the donor and an email notification to any control panel user with donation notifications enabled.
Our engineering team is investigating the best course of action for NationBuilder customers using Payflow. In the meantime, we strongly recommend that you disable monthly receipts if you have donors with longstanding recurring donations (i.e., beginning in 2015). This will prevent the delivery of misleading email receipts for backfilled recurring donations.