Microsoft 365 eDiscovery: 2026 Guide for IT & Legal Teams

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:

• Exchange Online (emails)
• SharePoint Online & OneDrive (documents)
• Microsoft Teams (chats, meetings, files)
• Outlook (mailboxes)
• Other Microsoft 365 apps (Yammer, etc.)

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:

• Create cases to organize searches
• Place content locations on legal hold
• Run content searches across mailboxes, sites, and Teams
• Export search results for review

Limitations:

• No advanced review or culling tools
• No predictive coding or analytics
• Manual workflows for larger volumes

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:

• All Standard features, plus:
• Advanced indexing (handles errors better)
• Custodian management (track specific users/data sources)
• Review sets (dedicated space for analyzing collected data)
• Analytics (near-duplicate detection, email threading, themes)
• Predictive coding (machine learning to prioritize relevant docs)
• Redaction tools
• Audit logs (track who did what)

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:

1. Navigate to Permissions
2. Add users to the eDiscovery Manager role group

Roles available:

• eDiscovery Manager: Create and manage cases
• eDiscovery Administrator: Manage all cases organization-wide

Step 2: Create a Case

1. Go to Microsoft Purview compliance portal → eDiscovery → Standard
2. Click Create a case
3. Name the case (e.g., "Smith v. Company 2026")
4. Add a description and assign members

Step 3: Place Content on Hold

Prevent data from being deleted or altered:

1. Inside your case, go to Holds
2. Click Create
3. Select content locations:
   • Specific mailboxes (by user)
   • SharePoint sites
   • OneDrive accounts
   • Microsoft Teams (channels, chats)
4. Apply a query (optional) to narrow the hold scope
5. Save the hold

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

1. In your case, go to Searches
2. Click New search
3. Define:
   • Locations: Mailboxes, sites, Teams, etc.
   • Keywords: Use Boolean operators (AND, OR, NOT)
   • Conditions: Date ranges, senders, recipients, file types
4. Run the search
5. Review the search statistics (number of items, locations, size)

Example query:

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

Step 5: Export Search Results

1. Select your completed search
2. Click Export results
3. Configure export options:
   • Include all versions (for SharePoint)
   • De-duplicate emails
   • Export format (PST for emails, native files for documents)
4. Download the export package

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

Step 6: Review and Produce

After export:

• Load files into your review platform (if using one)
• Apply privilege reviews, redactions, or tagging
• Produce responsive documents to requesting parties

Microsoft 365 eDiscovery Pricing (2026)

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

eDiscovery (Standard)

• Included in:
  • Microsoft 365 E3
  • Microsoft 365 E5
  • Office 365 E3/E5
  • Microsoft 365 Business Premium
• Cost: No additional charge beyond your M365 subscription

eDiscovery (Premium)

• Included in:
  • Microsoft 365 E5
  • Microsoft 365 E5 Compliance
• Add-on for E3 users: Microsoft 365 E5 Compliance (~$12/user/month as of 2026)

Storage costs:

• Standard M365 storage is included (1TB per user + 10GB per license)
• If you exceed limits, additional storage costs ~$0.20/GB/month

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:

• Date ranges
• Custodian filters
• Specific keywords (not vague terms)

3. Leverage Analytics (Premium Only)

If you have Premium:

• Use email threading to eliminate duplicate conversations
• Run near-duplicate detection to group similar docs
• Apply predictive coding to prioritize relevant documents

4. Document Everything

Maintain detailed records of:

• When holds were placed
• Search queries used
• Who accessed data and when
• Export logs

This creates a defensible process if challenged in court.

5. Train Your Team

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

• IT knows how to preserve data
• Legal understands search capabilities and limitations
• HR knows when to escalate potential litigation

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

• Slack often contains critical business communications (deals, decisions, disputes)
• Courts increasingly demand Slack data in litigation
• Slack's native export tools are limited (JSON files, no search)

How to Handle Slack eDiscovery

If you need to preserve and search Slack data:

1. Export Slack data (via Slack's native tools or API)
2. Use a Slack-specific eDiscovery tool like ViewExport to:
   • Search Slack messages (by keyword, date, user)
   • Apply legal holds
   • Export to review platforms
   • Generate defensible reports
3. Coordinate Microsoft 365 and Slack discovery efforts to avoid gaps

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

• Microsoft Purview Compliance Portal: Centralized compliance management
• Data Loss Prevention (DLP): Prevent sensitive data leaks across M365 apps
• Information Protection: Classify and protect sensitive documents
• Insider Risk Management: Detect risky user behavior
• Communication Compliance: Monitor Teams/Exchange for policy violations
• eDiscovery (Premium): Advanced search, review, and analytics

What Slack Enterprise Grid Compliance Covers

• Enterprise Key Management (EKM): Customer-controlled encryption keys
• Data Loss Prevention (via integrations): Third-party DLP tools
• Legal Hold: Preserve data from deletion
• Discovery API: Export private channels and DMs for eDiscovery
• Audit Logs: Track user actions and admin changes
• Enterprise Mobility Management (EMM): Mobile device management

The Gap: Why You Need Both

M365 E5 Compliance does NOT cover:

• Slack messages, channels, or files
• Slack workspace audit logs
• Slack app integrations

Slack Enterprise Grid does NOT cover:

• Microsoft 365 emails, documents, or Teams chats
• OneDrive/SharePoint file activity
• Exchange calendar/mailbox data

Integration Best Practices

1. Unified Legal Hold Process

• Trigger holds in BOTH systems simultaneously when litigation is anticipated
• Use Microsoft Purview + Slack Discovery API in parallel
• Document hold notifications across both platforms

2. Coordinated Export Workflows

• Export M365 data via eDiscovery (Premium)
• Export Slack data via Discovery API or standard export
• Process both through ViewExport for unified search and review

3. Cross-Platform Search Strategy

• Define search terms that work across both systems
• Account for different communication styles (formal email vs. casual Slack)
• Use date ranges to correlate M365 and Slack activity

4. Compliance Reporting

• Combine M365 Purview reports with Slack audit logs
• Create unified dashboards showing compliance posture across both platforms
• Train compliance team on both systems

Cost Considerations

• M365 E5: ~$57/user/month (includes eDiscovery Premium)
• Slack Enterprise Grid: ~$15-25/user/month (includes Discovery API access)
• ViewExport (Slack processing): ~$250/month per workspace
• Total compliance stack: ~$72-82/user/month + ViewExport

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:

• When holds were issued and to whom
• Search methodology and iterative refinements
• Custodian interviews and data source identification
• Export logs and chain of custody
• Review protocols and privilege determinations

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:

• All custodians' data is captured
• Metadata (timestamps, edits, deletions) is preserved
• Export format is compatible with review tools
• Exports complete within reasonable timeframes

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?

• Small case (< 10,000 items): 30 minutes to 2 hours
• Medium case (10,000-100,000 items): 2-8 hours
• Large case (100,000+ items): 8-48+ hours

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:

1. Tag privileged documents during review
2. Create a privilege log
3. Use redaction tools to black out privileged content before production
4. Export privilege log separately

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:

• Document legal basis for processing (e.g., legal obligation, legitimate interest)
• Minimize data collection (only relevant custodians/date ranges)
• Notify data subjects if required under GDPR Article 14
• Delete data after litigation concludes (unless retention policy requires longer storage)

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

• Microsoft 365 eDiscovery provides built-in tools for searching, holding, and exporting data from Exchange, SharePoint, Teams, and more
• Standard vs. Premium: Use Standard for simple cases; upgrade to Premium for complex litigation with analytics needs
• Process matters: Document holds, searches, and exports to create a defensible workflow
• Don't forget Slack: Microsoft 365 eDiscovery doesn't cover Slack—use a dedicated tool like ViewExport
• Dual-platform compliance: Organizations using M365 E5 + Slack Enterprise Grid need coordinated eDiscovery workflows

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