I recently released a game on Early Access and have since received many emails from Steam curators, Twitch streamers, or YouTubers. They let me know their subscriber count and requested game keys. I sent them keys, but over 90% of them never responded and I discovered my game being sold on an unknown site. Obviously, as a solo developer with no marketing skills, their emails are hard to resist. How can I distinguish legitimate emails from phishing ones among these emails?