As soon as a company signs up to facebook for a marketing campaign, yes, the first step is to upload a list of all the emails of all of your customers so that f

As soon as a company signs up to facebook for a marketing campaign, yes, the first step is to upload a list of all the emails of all of your customers so that facebook can associate users with your emails and build look-alike audiences, advertising to people similar in one dimension or another to your existing customers I don't know about GDPR, but usually a company has your email after you do business with them, so you probably implicitly agreed at some "continue" button to let them use your email as a part of marketing campaigns.