If you are an End-customer, iZettle may share your data with the Merchant from which you made a purchase.
In other section, they say they literally collect everything about buyer (it’s a bit foggy as they do different paragraphs for Merchants and End Users, but yeah, they suck up data about users like vacuum).
Izettle can link purchases based on card details.
All three things combined mean one thing for me, @heatherbaden. you made purchase from another Merchant in the past, where your email had to be known. On the next purchase from this cafe, izettle found your card… found your profile, suggested new merchant “hey, we can try to opt in this user for marketing crap for you” aaand that’s how this email was born.