My email was opened by someone besides me — what now?

Two different scenarios: (A) Tracking pixel shows I opened your email — that's how standard email tracking works (Mailchimp, Sendinblue, HubSpot Sales, Mixpanel etc). Not necessarily bad — in commercial marketing allowed with consent. (B) Tracker indicates my email opened at strange location or time — can indicate hacked account, shared device, or relationship spying. For scenario A — want to block tracking? (1) Mail app set to "block remote content" — Gmail Settings → "Display External Images" → "Ask before displaying". Outlook + Apple Mail similar. (2) Plain text mode where possible. (3) Privacy-friendly mail client — Proton Mail, Tutanota — block by default. (4) Marketing mails with tracking = GDPR breach without consent → unsubscribe + complaint. For scenario B — suspicious pattern? (1) Check security events in account (Google: myaccount.google.com → Security → "Recent security events"). (2) Sign out all sessions. (3) Change password on clean device. (4) Enable 2FA (app-based, not SMS). (5) In family-member/partner context: also check physical device access — password app misuse or biometric. On stalking suspicion: Slachtofferhulp + Veilig Thuis. On hack: account-hacked protocol (see article).