[cproctor]

This is when you email the company's head of marketing and/or security expressing naive concern about hacking/phishing. "I received an email that looked like it's from your company, but I know it's not real because I didn't sign up for any of your lists."

[Nextgrid]

When I receive unsolicited marketing email I will often intentionally not unsubscribe and instead set up a rule (now that I know the sender address or some way to reliably identify their spam) to redirect any future messages to someone high up at their company or their GDPR data protection officer.