Microsoft shares workaround for Outlook freezes after January Windows updates

Microsoft confirms Outlook freezes after January updates, and points to OneDrive PST storage

Microsoft has published a temporary workaround for a frustrating Outlook issue that surfaced after January 2026 Windows security updates. In affected environments, the classic Outlook desktop client can hang and become unresponsive, and in some cases it will not reopen unless the process is terminated in Task Manager or the device is restarted. Users also report mail synchronization side effects, including messages being downloaded again and sent mail not appearing in Sent Items even though delivery succeeded.

What makes this incident notable is that Microsoft is treating it as part of a broader Windows regression tied to cloud-backed storage access. In its Windows release health messaging, Microsoft warns that some applications may become unresponsive or throw unexpected errors when opening files from or saving files to OneDrive or Dropbox. Outlook is specifically called out because of a common pattern in small business and legacy deployments: PST files stored inside OneDrive-synced folders.

Who is affected, and which updates are involved

Initial reports focused on Windows 11 systems, but Microsoft's current advisories describe a wider platform footprint. The core trigger is Windows updates released on or after January 13, 2026. For Windows 11, this aligns with KB5074109, and Microsoft references OS build 26100.7623 in the release health entry. For Windows 10, Microsoft also points to uninstalling the January update KB5073724 in environments where the issue reproduces.

The Outlook-specific Microsoft support advisory narrows the most common scenario: classic Outlook profiles using POP accounts, and profiles where PST files are present. Microsoft notes the issue may occur for any Outlook profile that has PSTs stored on OneDrive, even outside pure POP-only usage. If your organization still relies on PST-centric workflows, shared mailbox archives, or local history stored in PST files, you are more exposed to this class of failure than an Exchange Online or Microsoft 365 profile using OST caching.

Why PST files in OneDrive are the common failure point

From a systems perspective, PST files behave like database files. Outlook maintains frequent read and write operations, and it expects stable file locking semantics. OneDrive, meanwhile, is a sync engine sitting between applications and the physical disk. Depending on configuration, it may use placeholder files, background hydration, and continuous synchronization that can collide with applications that assume exclusive or predictable access patterns.

Microsoft's release health wording indicates the regression is not exclusively "an Outlook bug." The broader warning is about apps that interact with cloud-backed storage, and Outlook becomes a prominent example because PST files are often placed into OneDrive for convenience, backup, or roaming access. When the OS update changes the interaction between applications, the file system, and cloud-backed storage providers, Outlook's PST I/O pattern can become a stress test that fails visibly.

Microsoft's recommended workaround: move PST files out of OneDrive, use webmail temporarily

Microsoft's best-practice mitigation is simple in principle, even if it may be operationally painful: move PST files out of OneDrive. In practical terms, that means relocating the PST to a local path that is not under OneDrive synchronization, then ensuring Outlook is pointed at the new location.

If you need continuity while planning that move, Microsoft also recommends using webmail where available. For POP users, that typically means using the provider's web interface as a temporary front door to email while desktop Outlook stability is restored. This is not a perfect substitute for workflows based on local Outlook rules and PST archives, but it keeps business mail flowing without introducing additional instability.

A safe, IT-friendly way to implement the PST relocation

1. Identify whether the PST is inside OneDrive. A common path looks like a user profile folder under OneDrive, such as Documents or a dedicated Outlook Files folder that is included in OneDrive sync.

2. Terminate Outlook cleanly via Task Manager if it is in a frozen state, then ensure it is not restarting in the background.

3. Copy the PST to a local folder that is not synced, for example a dedicated directory under the user profile that OneDrive does not manage. The goal is to eliminate the cloud-backed storage layer from the PST access path.

4. Update Outlook's data file location in account or data file settings so Outlook references the new local PST.

5. Monitor whether the unresponsive behavior and mail sync anomalies stop when Outlook starts again.

In enterprise settings, the most scalable approach is to standardize a policy: PST files should not be stored in OneDrive-synced locations. Even after Microsoft ships a permanent fix, the architectural tension between continuous sync and PST database I/O makes this a recurring risk area.

The "last resort" option: uninstalling the January update, with clear security tradeoffs

Microsoft and third-party reporting both mention that uninstalling the January update can mitigate the symptoms. For Windows 11 environments, the KB to consider is KB5074109. For Windows 10, Microsoft references KB5073724 in scenarios where Windows 10 is involved. The removal process is performed from Settings, under Windows Update history and uninstalling the relevant update entry.

However, you should treat rollback as a risk-managed decision, not a default troubleshooting step. Security updates exist to close vulnerabilities, including flaws that may be exploited quickly after Patch Tuesday. If you choose to uninstall, compensate with additional controls where possible, such as tightening endpoint protections, restricting exposure of vulnerable services, and accelerating validation of the next cumulative update once Microsoft ships a fix.

For organizations that cannot tolerate Outlook downtime, an acceptable short-term strategy is often to apply Microsoft's workaround first, validate that the PST relocation stabilizes Outlook, and keep the security update installed. That preserves patch coverage while addressing the operational impact.

What to watch next

Microsoft lists this issue as confirmed and says it is working on a resolution "as soon as possible." There is no committed ETA in the public advisories. The most reliable place to track status changes is the Windows release health dashboard entry for "Apps might become unresponsive when saving files to cloud-backed storage," which Microsoft is actively updating with timestamps.

If you are managing multiple endpoints, document the affected configuration patterns now: POP accounts, PST usage, and PST paths under OneDrive. That evidence will be useful for support escalation and for preventing future recurrences. Until Microsoft ships a fix, the practical reality is that stabilizing Outlook means reducing dependency on cloud-synced PST storage and using webmail as a temporary fallback when needed.