I run AliasFleet , an email-alias service. One of its features, vendor leak detection, answers a question every developer has asked at least once: which site leaked my address? The mechanism behind it is simple, and that is the point. Let me walk through how it works under the hood. Your address is a join key Think of your single email address the way you would think of a database key. It appears in the users table of every service you ever signed up for. When any of those datab...