As an Information Security Consultant currently advising small and mid-sized organizations on migrating from legacy suites (specifically Microsoft 365 E3/E5) to privacy-first, sovereign European alternatives. While Proton’s zero-knowledge architecture is the gold standard for data confidentiality, my risk assessments consistently identify a significant gap in Data Loss Prevention (DLP) capabilities for Business and Visionary tiers.

Current compliance frameworks (GDPR Article 32, ISO 27001, SOC 2) require not just encryption at rest/in transit, but active controls against accidental or malicious exfiltration of sensitive data (PII, PHI, PCI-DSS).

Proton excels at preventing external interception. However, it lacks the ability to inspect outbound content for sensitive patterns before encryption or during the sharing workflow. Without native DLP, organizations cannot enforce policies to block the accidental sharing of unencrypted sensitive data via email or Drive links, nor can they generate audit logs for compliance reporting regarding data movement.

To make Proton a viable "drop-in" replacement for M365 Enterprise in regulated sectors, I recommend implementing:
- Pattern-Based Detection: Regex matching for sensitive data types (e.g., IBANs, SSNs, Passport IDs) on outbound emails and file uploads.
- Policy Engine: Granular admin controls to "Block," "Quarantine," or "Warn" users based on data classification.
- Audit & Reporting: Detailed DLP event logging in the Admin Console to satisfy compliance auditors.
- Contextual Awareness: Ability to apply policies based on recipient domain (e.g., block external sharing of "Confidential" tagged files).

DLP is the missing link between Proton's privacy excellence and enterprise readiness. Adding this capability would unlock immediate demand from regulated industries and eliminate the need for a hybrid M365/Proton deployment. I strongly encourage prioritizing this on the roadmap..