Why is my Outlook New favorites list missing mailbox names and not syncing?

Is Outlook New broken for anyone else managing multiple shared inboxes right now?

Impact Assessment: High
Affected Version: 1.2025.1209.500
Date Detected: January 6, 2026

If you rely on Outlook New to manage multiple email accounts or shared mailboxes, you need to be aware of a breaking bug introduced in the latest update. This specific version renders the client unstable for professional workflows that depend on the “Favorites” feature for organization.

The Technical Issue

An update deployed on January 6, 2026, corrupted how Outlook New handles display logic for pinned folders. The error specifically targets users who consolidate multiple inboxes (e.g., personal, work, and shared service accounts) into their Favorites sidebar.

Diagnostic Symptoms

You can confirm if your installation is affected by checking for these three simultaneous failures:

1. Loss of Mailbox Identification: Previously, pinning a folder like “Inbox” displayed the specific account name in parentheses, such as Inbox ([email protected]). The current bug strips this identifier. You will see only generic labels like “Inbox,” making it impossible to distinguish between accounts at a glance.
2. Synchronization Failure: This is the most critical operational failure. New incoming emails do not appear in these compromised Favorite folders. The view remains static, hiding urgent communications.
3. Drag-and-Drop Malfunction: Attempting to manually move emails into these Favorite folders fails. The interface no longer registers the drop action, disrupting standard filing workflows.

Scope and Origins

Reports confirm this issue is not isolated. It impacts the Windows client version 1.2025.1209.500. The bug appeared suddenly on January 6, 2026, affecting service providers and professionals who manage shared mailboxes for teams.

Microsoft Support has validated that this specific version number correlates with the reported failures. However, support tickets indicate that while the engineering team identified the faulty build, no immediate patch or workaround exists within the Outlook New client itself.

Operational Recommendations

Until Microsoft deploys a hotfix, the Outlook New client is functionally unusable for multi-mailbox management. To maintain business continuity, I advise the following temporary measures:

1. Switch Clients: Revert to “Classic Outlook” (Win32 application) if your license permits. The classic architecture handles shared mailboxes differently and remains stable.
2. Use Web Access: Log in to Outlook on the Web (OWA). The browser-based version does not share the specific code base causing this rendering error and displays shared folders correctly.
3. Avoid Re-installing: Do not waste time reinstalling the application. Since the bug is inherent to the current version pushed by Microsoft servers, a fresh install will simply reintroduce the same flawed code.