How NIS2 and HIPAA are reshaping email and collaboration security standards for CISOs

The regulatory push

Regulators are responding to this shift. HIPAA’s privacy and security rules, long focused on protecting PHI in email, now apply just as much to data exchanged in chat, video meetings, and cloud file repositories.

In Europe, NIS2 is raising the bar across critical sectors, requiring organizations to prove resilience, report cyber incidents quickly, and ensure supplier oversight. Even outside regulated industries, PCI DSS v4.0 is setting the tone by making DMARC enforcement a requirement, forcing companies to authenticate every sender before enforcement deadlines take effect.

“Even if Slack or Teams aren’t named explicitly in the regs, the message is clear,” says Andrew Williams, Mimecast’s Principal Product Marketing Manager. “You need to secure sensitive data wherever it travels, whether that’s in an email, a chat message, or a shared file.”

The shift to unified controls

Five years ago, most security teams treated collaboration platforms as internal spaces and relatively low risk. That’s no longer defensible. Attackers are exploiting stolen credentials and OAuth tokens to gain persistent access.

Forward-leaning CISOs are converging their controls:

• Telemetry: Linking email and collaboration data to spot risky behavior across channels.
• Identity: Enforcing MFA and least privilege consistently across mailboxes and Teams/Slack identities.
• AI-Powered Detection: Flagging anomalies in chats, links, and file shares before they escalate into incidents.

This shift is as much cultural as it is technical. SOC analysts, compliance teams, and IT admins need to see phishing attempts and data exfiltration attempts in a single pane of glass, not in separate tools that require manual correlation.

What’s required right now

HIPAA

HIPAA already demands risk analysis, access controls, encryption, audit logging, and workforce training. Now that data is scattered across multiple platforms, those controls must apply across the board.

NIS2

NIS2 mandates organizational risk management, business continuity plans, supplier risk oversight, and near-real-time incident reporting. The burden on CISOs is clear: be able to prove resilience and respond to a breach, across all communication channels, without disrupting operations.

Together, HIPAA and NIS2 are pushing CISOs toward a single, unified approach that covers email, chat, and collaboration environments.

CISO priorities for 2025

1. Human risk management goes cross-channel

Mimecast’s 2025 State of Human Risk Report found that just 8% of users cause 80% of security incidents.

The solution isn’t locking everything down, it’s risk-based intervention.

Mimecast’s platform scores user behavior across email, Slack, Teams, and SharePoint, then applies adaptive policies and micro-trainings to “cushion” users against mistakes without impacting productivity.

2. AI-driven pre-delivery and in-flow defenses

Phishing isn’t confined to email. Teams chats, OneDrive links, and even Zoom invites are being weaponized. Mimecast’s AI engine scans messages, URLs, and attachments before they reach the user, catching threats early and reducing the need for noisy post-delivery cleanup.

3. Treat collaboration platforms as first-class citizens

Attackers don’t care if a message lives in an inbox or a chat thread, and neither should your defenses. CISOs are now:

• Applying DLP and scanning to Slack, Teams, SharePoint, and OneDrive.
• Enforcing policy controls for sensitive file sharing and unsanctioned uploads.
• Centralizing retention and logging to speed compliance reporting and eDiscovery.

Mimecast Collaboration Security brings all of this under one roof, giving organizations a consistent defense layer across channels.

4. Get ahead of insider risk and data exfiltration

Insider risk isn’t always malicious, but it’s almost always costly. In 2025, the biggest risks are coming not just from disgruntled employees, but from accidental data exposure and “Shadow IT”, those unsanctioned apps and AI tools that employees connect to corporate systems without security review.

Mimecast research shows that even well-meaning employees can inadvertently leak sensitive data by uploading files to personal cloud storage or granting over-permissive access to generative AI tools.

These blind spots make it easy for attackers to siphon off data once they’ve gained a foothold.

What CISOs should do next:

• Detect risky behaviors in real time: Monitor for unusual file transfers, mass downloads, or employees forwarding sensitive documents to external accounts.
• Flag unsanctioned app connections: Automatically identify OAuth grants to risky third-party apps and revoke them before data is exposed.
• Secure the offboarding process: Ensure accounts are disabled promptly, shared links are revoked, and access keys are rotated when employees leave.

Automation is key here. When suspicious activity is spotted, Mimecast’s platform can automatically quarantine files, revoke permissions, and notify security teams, while maintaining an auditable trail for compliance reporting. That audit trail isn’t just for regulators; it also helps legal and HR teams understand the intent behind an incident and respond appropriately.

5. Mature data governance and eDiscovery

When a regulator or legal team requests evidence, time is not on your side. HIPAA and NIS2 expect organizations to produce email and collaboration data quickly, consistently, and in a legally defensible way.

That’s where mature data governance comes in. Retention policies must be channel-agnostic, covering not only email but Slack messages, Teams chat logs, and files shared on SharePoint and OneDrive. If data is scattered across silos, or worse, deleted prematurely, organizations risk fines, lawsuits, and reputational damage.

Mimecast Archiving provides immutable, tamper-proof storage with rapid, federated search capabilities.

This allows legal teams and incident responders to:

• Place legal holds instantly across multiple communication channels.
• Run complex searches across billions of messages and files in seconds.
• Produce defensible records for auditors, regulators, or courts, with chain-of-custody intact.

The real advantage isn’t just compliance, it’s speed. In the middle of a breach investigation, time saved on discovery translates directly to faster containment and lower business impact.

6. Enforce DMARC and authentication

DMARC used to be optional. Not anymore. With PCI DSS v4.0 and mailbox providers moving toward stricter enforcement, DMARC is now essential for both compliance and deliverability.

DMARC (Domain-based Message Authentication, Reporting & Conformance) works alongside SPF and DKIM to authenticate every message sent from your domain. Moving from p=none (monitor-only) to p=reject ensures spoofed emails are blocked before they reach your customers, partners, or employees.

But DMARC isn’t just about stopping brand impersonation, it’s a trust signal. Executives are increasingly asking CISOs to translate DMARC metrics into business outcomes:

• Fewer BEC incidents: Reducing spoofed executive emails means fewer financial fraud attempts.
• Higher deliverability: Marketing and HR communications are less likely to end up in spam.
• Regulatory confidence: Demonstrating authenticated mail flow satisfies auditors and reduces risk exposure under NIS2 and HIPAA (when patient or customer data is involved).

Mimecast’s DMARC Analyzer automates sender discovery, aligns SPF/DKIM/DMARC records, and provides detailed reporting to guide organizations through enforcement, without breaking legitimate mail flow.

How to roll this out

First 90 days

• Inventory all email and collaboration tenants, connectors, and data flows.
• Baseline risky behaviors and publish DMARC in monitor mode.
• Deploy visibility into Teams, Slack, and SharePoint to catch unauthorized access early.

90–180 days

• Progress DMARC toward enforcement.
• Expand file and URL scanning in collaboration tools.
• Roll out insider-risk detections and automated response workflows.

180+ days

• Standardize retention and legal hold policies across platforms.
• Rehearse incident reporting to meet NIS2’s strict timelines.
• Iterate training and adaptive policies based on telemetry and near-misses.

Framing the conversation for the board

When CISOs brief executives, the message needs to be simple: unified controls over email and collaboration aren’t optional, they’re required for compliance, continuity, and brand trust.

Boards want metrics: fewer phishing-driven incidents, faster response times, and lower regulatory exposure. A consolidated platform also reduces tool sprawl and improves employee experience, a win that resonates outside the SOC.

Staying ahead

Email and collaboration security are converging, and so are the risks. HIPAA, NIS2, and PCI DSS v4.0 are turning guidance into obligation.

Mimecast gives CISOs a single platform to manage AI-driven detection, human risk scoring, and governance across email, Teams, Slack, SharePoint, and beyond.

Schedule a demo today and see how Mimecast can help your organization get compliant, stay resilient, and stop threats before they spread.

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