Microsoft Purview for eDiscovery: Benefits, Limitations, and Best Practices

Microsoft Purview, integrated within the Microsoft 365 suite, offers in-house legal teams a centralized platform for managing legal holds and eDiscovery processes. Its seamless integration with existing IT infrastructure and the potential cost savings compared to third-party tools make it an attractive option. However, relying solely on Purview for legal holds and discovery can expose organizations to significant risks, especially in high-stakes or time-sensitive matters.

Licensing Limitations​

Microsoft Purview's eDiscovery capabilities are tiered across different licensing levels:

• Content Search: Basic search and export functionalities.
• eDiscovery (Standard): Adds case management and legal hold capabilities.
• eDiscovery (Premium): Offers advanced features like custodian management, analytics, and predictive coding.

Access to these advanced features requires an E5 license or equivalent add-ons, which can be cost-prohibitive for some organizations. Without these features, legal teams may lack essential tools for comprehensive eDiscovery, potentially compromising the defensibility of their processes. (cloudficient.com)

Data Scope and Integration Challenges​

Purview primarily focuses on data within the Microsoft 365 environment, such as emails, OneDrive, and SharePoint. However, many organizations utilize a variety of third-party applications like Slack, Google Drive, and Zoom. Purview's limited support for these external data sources can result in incomplete data collection, posing risks of under-collection and potential legal challenges. (attorneyatwork.com)

Indexing and Search Performance Issues​

Purview's indexing capabilities have notable limitations:

• Partial Indexing: Large files or those with numerous attachments may be only partially indexed or skipped entirely, leading to unsearchable data.
• Slow Indexing and Search: The system's indexing throughput is approximately 2GB per hour, and search performance degrades with larger datasets. For instance, searching 100,000 mailboxes can take up to 25 minutes per search.

These performance issues can delay legal proceedings and increase the risk of missing critical information. (arctera.io)

Limited File Type Support​

Purview supports a limited number of file types, predominantly Microsoft-native formats. This narrow compatibility can be problematic for organizations dealing with diverse data formats, necessitating additional tools or manual processes to handle unsupported files, thereby increasing costs and complexity. (cloudficient.com)

Audit Trail and Defensibility Concerns​

Maintaining a defensible eDiscovery process requires comprehensive audit trails and consistent metadata handling. Purview's audit logs may be incomplete or lack sufficient detail, and metadata inconsistencies in exports can challenge the authenticity and admissibility of evidence in court. These issues can undermine the defensibility of the eDiscovery process. (cloudficient.com)

Inactive Mailboxes and Data Retention Risks​

Managing inactive mailboxes in Microsoft 365 presents additional challenges:

• Limited Visibility: Identifying and managing inactive mailboxes is cumbersome, with Purview displaying a maximum of 5,000 inactive mailboxes, even if more exist.
• Storage Costs: As of January 27, 2025, Microsoft began charging storage fees for inactive accounts on retention and legal holds, potentially leading to unexpected costs.

Without proper management, organizations may face increased legal exposure and financial burdens. (blog.x1discovery.com)

Recommendations​

To mitigate these risks, organizations should consider the following:

• Evaluate Licensing Needs: Assess whether the advanced features in eDiscovery (Premium) justify the additional licensing costs or if third-party solutions offer better value.
• Integrate External Data Sources: Implement solutions that can seamlessly collect and process data from both Microsoft 365 and third-party applications.
• Enhance Indexing and Search Capabilities: Utilize tools that offer faster and more comprehensive indexing and search functionalities to handle large datasets efficiently.
• Expand File Type Support: Ensure the chosen eDiscovery solution can process a wide range of file formats to avoid data loss.
• Maintain Robust Audit Trails: Implement systems that provide detailed and consistent audit logs to support the defensibility of the eDiscovery process.
• Manage Inactive Mailboxes Proactively: Regularly audit and manage inactive mailboxes to control storage costs and reduce legal risks.

While Microsoft Purview offers a convenient and integrated approach to eDiscovery within the Microsoft 365 ecosystem, its limitations necessitate a careful evaluation. Organizations should assess their specific needs and consider supplementing Purview with additional tools or processes to ensure a comprehensive, efficient, and defensible eDiscovery strategy.

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Source: Law.com The Hidden Risks of Relying on Microsoft Purview for Legal Holds and Discovery | Law.com