Microsoft 365 eDiscovery Guide for IT, Legal & HR

Microsoft 365 eDiscovery, formerly Office 365 eDiscovery, is the process of identifying, collecting, and managing content across your Microsoft cloud environment for legal discovery, compliance investigations, and regulatory requests.

This 2026 guide walks IT administrators, legal teams, and compliance officers through Microsoft 365's eDiscovery tools, workflows, and best practices. We'll also touch on how communication platforms like Slack fit into a broader eDiscovery strategy.

What Is Microsoft 365 eDiscovery?

Microsoft 365 (M365) eDiscovery refers to capabilities built into Microsoft's ecosystem to search, collect, and preserve electronic data from across Microsoft 365 services, including:

The goal is to identify relevant content for legal holds, litigation, audits, internal investigations, or regulatory compliance.

These tools help organizations respond efficiently to discovery requests without manually combing through terabytes of data or disrupting normal operations.

Microsoft 365 eDiscovery Tools Overview

Microsoft offers two main eDiscovery solutions in 2026:

1. eDiscovery (Standard)

Best for: Smaller cases, basic search and export needs.

Key features:

Limitations:

Who should use it: Organizations handling occasional, low-volume cases without the need for advanced analytics.

2. eDiscovery (Premium)

Best for: Complex, high-volume cases requiring advanced features.

Key features:

Who should use it: Organizations dealing with litigation, complex investigations, or regulatory obligations that demand defensible, efficient workflows.

Step-by-Step: Running an eDiscovery Case in Microsoft 365

Here's how to run a typical eDiscovery case using eDiscovery (Standard):

Step 1: Assign Permissions

Before starting, ensure the right people have access.

In the Microsoft Purview compliance portal:

Roles available:

Step 2: Create a Case

Step 3: Place Content on Hold

Prevent data from being deleted or altered:

Pro tip: Be as precise as possible with holds to avoid preserving unnecessary data, which increases storage costs and review time.

Step 4: Run a Content Search

Example query:

(contract OR agreement) AND (date:01/01/2025..12/31/2025)

Step 5: Export Search Results

Note: Large exports can take hours. Microsoft sends an email notification when ready.

Step 6: Review and Produce

After export:

Microsoft 365 eDiscovery Pricing (2026)

Microsoft 365 eDiscovery licensing can be confusing. Here's the breakdown:

eDiscovery (Standard)

eDiscovery (Premium)

Storage costs:

Best Practices for Microsoft 365 eDiscovery

1. Implement a Legal Hold Policy Early

Don't wait until litigation starts. Create automated hold policies in Microsoft Purview to trigger holds based on events (e.g., employment termination, contract disputes).

2. Use Targeted Searches

Broad searches = wasted time and costs. Use:

3. Leverage Analytics (Premium Only)

If you have Premium:

4. Document Everything

Maintain detailed records of:

This creates a defensible process if challenged in court.

5. Train Your Team

eDiscovery isn't just a tool—it's a process. Ensure:

Beyond Microsoft 365: What About Slack?

Many organizations use both Microsoft 365 and Slack. Here's the problem:

Microsoft 365 eDiscovery does NOT cover Slack.

If your organization uses Slack for internal communication, you need a separate eDiscovery solution for Slack data.

Why Slack Matters in eDiscovery

How to Handle Slack eDiscovery

If you need to preserve and search Slack data:

M365 vs Slack eDiscovery: Side-by-Side Comparison

Key Insight: Most organizations need BOTH solutions. Microsoft 365 handles your formal documentation, while Slack captures rapid decision-making and informal discussions that often become critical in litigation.

Learn more: Contact us to see how ViewExport handles Slack eDiscovery alongside your Microsoft 365 workflows.

Enterprise Grid + M365 E5: Compliance Overlap & Integration

Organizations using both Slack Enterprise Grid and Microsoft 365 E5 have overlapping compliance capabilities but must coordinate both platforms for comprehensive eDiscovery.

What M365 E5 Compliance Covers

What Slack Enterprise Grid Compliance Covers

The Gap: Why You Need Both

M365 E5 Compliance does NOT cover:

Slack Enterprise Grid does NOT cover:

Integration Best Practices

1. Unified Legal Hold Process

2. Coordinated Export Workflows

3. Cross-Platform Search Strategy

4. Compliance Reporting

Cost Considerations

Alternative: Organizations on M365 E3 + Slack Business+ spend less but have limited eDiscovery capabilities (no Premium analytics, no Slack DM exports).

Common Pitfalls to Avoid

1. Not Placing Holds Fast Enough

Data can be deleted quickly (especially in Teams chats). Place holds immediately when litigation is reasonably anticipated.

Real consequence: In Orbit One Commc'ns, Inc. v. Numerex Corp., failure to preserve ESI resulted in $2.7 million in sanctions.

Fix: Create automated hold policies in Microsoft Purview that trigger on specific events (employment termination, contract dispute notification, subpoena receipt).

2. Over-Collecting Data

Collecting too much data increases costs and review time. Be strategic with custodians and date ranges.

Cost impact: Reviewing 1TB of data costs ~$10,000-$50,000 in legal fees. Over-collection can double or triple this.

Fix: Use custodian interviews to identify key players, then narrow searches by date range (±6 months around key events) and specific data sources.

3. Ignoring Non-Microsoft Data Sources

Don't forget Slack, Zoom, Google Workspace, or other third-party apps your org uses.

Blind spot: If 80% of team communication happens in Slack but you only preserve M365, you've missed the most relevant evidence.

Fix: Conduct a communication audit to identify all platforms in use, then establish eDiscovery protocols for each.

4. Poor Search Queries

Vague keywords = massive result sets. Work with legal counsel to refine queries.

Bad query: "contract"

Better query: (contract OR agreement) AND (Smith OR "ABC Corp") AND (date:01/01/2025..06/30/2025)

Fix: Use Boolean operators, quoted phrases, date ranges, and field-specific searches (subject:, from:, etc.)

5. Lack of Documentation

If you can't prove your process was defensible, opposing counsel will challenge it.

What to document:

Fix: Maintain a case chronology document updated throughout the eDiscovery process.

6. Not Testing Exports Before You Need Them

Many teams discover their export process is broken only when under litigation pressure.

Risk: Incomplete exports, missing metadata, corrupted files, or inaccessible formats.

Fix: Run quarterly test exports and verify:

7. Assuming M365 Captures Everything

Microsoft Teams chats can be deleted by users (depending on settings). OneDrive files can be permanently removed after 93 days in recycle bin.

Fix: Configure retention policies to automatically preserve data beyond user-controlled deletion periods.

8. Neglecting Mobile Device Data

Employees use Outlook mobile, Teams mobile, and OneDrive mobile—data on these devices may not sync immediately.

Fix: Include mobile device data sources in holds and coordinate with IT for Mobile Device Management (MDM) policies.

Frequently Asked Questions

What's the difference between eDiscovery (Standard) and (Premium)?

Standard is included in M365 E3 and provides basic search, hold, and export capabilities. Premium (E5 only) adds advanced analytics, predictive coding, custodian management, and review sets. Use Standard for straightforward cases; upgrade to Premium for complex litigation requiring machine learning and advanced culling.

Can I use Microsoft 365 eDiscovery for Slack data?

No. M365 eDiscovery only works with Microsoft 365 data sources (Exchange, SharePoint, Teams, OneDrive). For Slack, you need a separate solution like ViewExport.

How long does a typical M365 eDiscovery export take?

Large exports are queued and processed in batches. Microsoft emails you when ready.

Do I need E5 licenses for everyone, or just eDiscovery users?

You need E5 (or E5 Compliance add-on) licenses for data custodians whose data you want to search/export, NOT for the people performing the search. However, most orgs find it easier to license everyone at the same tier.

Can opposing counsel request my M365 eDiscovery audit logs?

Yes. Courts increasingly demand transparency in eDiscovery processes. Your audit logs (who searched what, when) can be subject to discovery if opposing counsel argues your methodology was biased or incomplete.

What happens to Teams messages when users are deleted?

If retention policy is enabled: Messages are preserved even after user deletion.

If no retention policy: Messages remain visible in Teams but may be lost if the team/channel is deleted.

Best practice: Enable retention policies BEFORE litigation is anticipated.

Can I export Teams meeting recordings via eDiscovery?

Partially. Teams meeting recordings stored in OneDrive/SharePoint are captured by eDiscovery. However, meeting transcripts and participant metadata require separate extraction methods.

How do I handle privileged content in M365 exports?

Use eDiscovery (Premium) to:

For Standard users, load exports into third-party review platforms (Relativity, Everlaw) for privilege review.

Is M365 eDiscovery GDPR compliant?

Yes, but with caveats. You must:

Can I search deleted emails in Exchange Online?

Yes, if they're still in the user's Deleted Items or Recoverable Items folder (retained for 30 days by default, or longer if litigation hold is enabled). Permanently deleted emails (hard-deleted) are only recoverable if a hold was in place at the time of deletion.

Key Takeaways

Need help managing eDiscovery across Microsoft 365 and Slack? Reach out to see how ViewExport complements your M365 strategy.