The **email address** on your PSN account is your **primary account identifier and recovery anchor**. It serves four critical functions:
Your **Sign-In ID** = this email. You cannot log in with your Online ID (gamertag) on web/app — only email.
Transaction history tied to this email is your **proof of purchase** for refunds, disputes, or support tickets.
Bottom line: Treat this email like the master key to your digital library. Secure it (2FA on email provider), keep it current, and never share it.