I've done something similar for years. Every site gets a unique email address that follows a specific patters (e.g. [email protected]). Most of the sites don't sell or leak my email addresses. It has happened, but the majority of the email addresses I've generated (close to a thousand) do not get spammed. I'd say less than 1%. Most of the spam coming to my domains are to generic addresses like [email protected] or to addresses I didn't populate like [email protected].