What is this strange Apple email address I can see for a supporter?

Apple ID is one of the options available when setting up sign in details for Stewardship accounts. One of the features that Apple provides gives users the option of hiding their email address. If a giver has chosen to do this their email address will show with a string of letters and numbers @privaterelay.appleid.com. Apple uses these addresses to forward emails on, so you can still use this address to contact your supporter.