Topic starter
14/07/2026 4:20 pm
TL;DR: A regional financial institution found that strengthening Microsoft Purview DLP exposed broader blind spots in internal email visibility, lateral phishing, and data exfiltration workflows, according to Proofpoint. The lesson is that DLP projects fail when email security, investigation speed, and data protection operate as separate control planes.
Editorial analysis by NHI Mgmt Group, based on content published by Proofpoint: “How a financial institution closed email security gaps by replacing Mimecast with Proofpoint”.
Key questions
Q: What fails when DLP cannot see internal email abuse?
A: DLP fails as a governance control when it cannot observe user-to-user email, because the attack path becomes invisible even if the content is policy-checked.
Q: Why does email visibility matter so much for regulated environments?
A: Regulated environments need to prove that data movement is controlled, not just blocked at the perimeter.
Q: What are the signs that email security and DLP are too fragmented?
A: Common signs include slow investigations, inconsistent detection of internal threats, repeated manual correlation across tools and weak confidence in whether a suspicious message was contained.
Practitioner guidance
- Map internal email visibility gaps Identify where your current DLP and email security stack cannot trace user-to-user communication, message history or post-delivery abuse across Microsoft 365.
- Correlate email events with identity state Link suspicious messages to account behaviour, authentication anomalies and mailbox actions so compromised identities are visible in the same investigation workflow.
- Measure investigation and remediation latency Track how long analysts need to scope a suspicious email, contain it and verify that follow-on risk has been removed from the environment.
Bottom line: The article shows that DLP can look effective on paper while internal email abuse, lateral phishing and exfiltration remain under-observed.
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14/07/2026 4:35 pm
Email visibility is now a DLP control, not a separate monitoring layer. If security teams cannot trace internal message flow, DLP becomes a partial control that misses the path of abuse even when it inspects the content correctly. That is especially true in Microsoft 365 environments where authenticated internal communication is the primary attack surface. Practitioners should treat message traceability as part of data protection governance, not an optional add-on.
A few things that frame the scale:
- Only 5.7% of organisations have full visibility into their service accounts, according to the Ultimate Guide to NHIs.
A question worth separating out:
Q: How should identity teams connect email security to broader access protection?
A: Identity teams should treat phishing as an access-risk event, not only a messaging issue. Suspicious email activity should feed account, session, and mailbox monitoring so response can begin before credentials are reused or delegated access is abused. That makes the email layer part of the identity control stack.
👉 Read our full editorial: Email security visibility gaps are undermining DLP programmes