Mistakes happen. You send a bulk email to CC rather than BCC. You email out contacts that have unsubscribed. You accidentally click on a malicious link.
Render the data you keep useless to anyone outside of your organization.
Default compliance with GDPR, CCPWA, Privacy Act, PIPEDA, HIPPA.
Program in your compliance & email opt-in status. Audit emails by recipient. Securely share data with vendors & apply self-detonation to the data.