By Chas Meier and John Patzakis
In our recent blog post, we outlined the challenges associated with inactive mailboxes in Microsoft 365. The response was very positive, and this post dives a bit deeper into the specific challenges with MS Purview in addressing inactive mailboxes, including some hidden pitfalls and risks that many enterprises may not be aware of.
Limited Visibility in Microsoft Purview
Microsoft Purview allows users with the eDiscovery Manager role (each provisioned with an E5 license) to search both active and inactive mailboxes to meet legal or regulatory requirements. However, one of the first hurdles administrators face is simply identifying which mailboxes are inactive. Inactive mailboxes do not appear in the standard active user lists and require additional steps to locate, whether through Purview or the Microsoft 365 admin center. An even bigger challenge is Purview’s limitation: when you query for inactive mailboxes, it will only display a maximum of 5,000—even if more exists. One of our customers, for example, discovered tens of thousands of additional inactive mailboxes using X1, far exceeding Purview’s 5,000 limit. Compounding this challenge, Purview cannot distinguish between an inactive mailbox placed on litigation hold versus one on a retention tag for other reasons, leaving organizations unable to quickly determine which mailboxes are truly subject to legal holds.
How Inactive Mailboxes Are Created
This problem partly stems from Microsoft 365’s process for creating inactive users. Under pressure to free up M365 licenses for new employees, administrators might place holds or retention tags on a departing user’s account “just to be safe” until they know how to manage that user’s data. Once the license is removed, a grace period begins; after it expires, the mailbox is moved into the inactive mailbox collection, ensuring its contents remain discoverable for eDiscovery and compliance purposes.
However, there is no built-in mechanism to automatically remove these holds once they are no longer needed, so IT and legal teams must manually intervene. As a result, organizations with high turnover often retain far more inactive mailboxes than necessary. This not only increases legal exposure but will also incur additional costs when Microsoft begins charging storage fees on January 27, 2025 for inactive M365 accounts on retention and legal holds. (Manage unlicensed OneDrive user accounts – SharePoint in Microsoft 365 | Microsoft Learn)
X1 Enterprise 5.3: A Streamlined Approach
With X1 Enterprise 5.3, legal and compliance professionals can now process inactive mailboxes directly within the platform using only a single E5 license and are not subject to Purview’s listing limit of 5,000 inactive mailboxes. This direct integration ensures that all preserved mailboxes are accessible and actionable.
Even better, many of our customers employ X1 Enterprise to proactively perform targeted preservation collections on M365 accounts and other sources such as laptops for departing employees, a streamlined process that significantly reduces both cost and risk.
Please contact us at the link below if you have any additional questions about inactive mailboxes in M365 and would like to inquire about a free “health check” assessment of the scope of your inactive mailboxes.
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