Microsoft has confirmed it is working on a fix for a bug affecting Classic Outlook, the traditional desktop email and calendar app that remains the default client for many Office and Microsoft 365 users.
According to Neowin, the Outlook Team is developing a hotfix to resolve the issue, though the company hasn’t said when it will arrive or exactly what triggers the problem.
Affected versions: Not officially specified (Classic Outlook desktop app).
Error code / KB: Not published yet.
Here’s what we know so far, how Microsoft typically handles these situations, and what you should do in the meantime.
What we know about the bug
The one concrete detail Microsoft has shared is that affected users are seeing error messages while using Classic Outlook. That is the full extent of what’s been confirmed so far.
The company hasn’t yet explained what those error messages actually say, which actions or features trigger them, or which specific build of Classic Outlook is impacted. Without those details, it’s hard to judge how widely the problem is spreading or how many users are actually affected.
For context, Classic Outlook is the long-standing desktop client that ships with Microsoft 365 and Office 2021, 2019, and other licensed versions. It’s distinct from the newer, browser-based “New Outlook,” which Microsoft has been encouraging users to adopt over the past couple of years. Many organizations and power users still lean on the classic app because of its fuller feature set, deeper customization, and support for add-ins that the new version doesn’t yet match.
That reliance is exactly why bugs in Classic Outlook tend to draw attention: a large base of professional users depend on it for day-to-day work, so even a narrow issue can ripple across teams.
How Microsoft usually fixes Outlook bugs
When a bug surfaces in Classic Outlook, Microsoft typically responds through its regular update pipeline. Widespread issues often get a targeted hotfix that can ship faster than the standard monthly update, which is what the Outlook Team appears to be doing here.
These fixes generally roll out through the Office update mechanism — the Click-to-Run updater that Microsoft 365 and Office use — and can be pushed either automatically or through enterprise management tools like Intune or WSUS, depending on how an organization has configured its update channels.
That said, Microsoft doesn’t always publish a formal support article or KB number for every Outlook issue. Smaller or more targeted bugs are sometimes resolved quietly through a hotfix without a public changelog entry, which fits the situation here given that no KB ID or error code has been released.
What this means for you
If you use Classic Outlook and haven’t encountered the error, there’s nothing for you to do right now. The issue appears to affect only a subset of users, so most people will simply keep working as usual.
If you are seeing error messages, the practical first step is to make sure your app is up to date. Open Classic Outlook, go to File > Office Account > Update Options > Update Now, and let it pull in the latest build. Sometimes a fresh update clears the glitch outright.
If the error persists after updating, your best move is to report it directly to Microsoft. Within Outlook, you can navigate to File > Feedback > Send Feedback and describe the problem, including any error text you’re seeing. Reporting helps the Outlook Team prioritize and reproduce the issue, which speeds up the fix.
How to get the fix
Once the Outlook Team finishes the hotfix, it should reach Classic Outlook users through the normal Office update flow — meaning you’ll typically receive it automatically without having to do anything special.
To make sure you get it promptly, keep automatic updates enabled. If you’re on a managed device at work, your IT team controls the update schedule, so the fix may arrive on their timeline rather than yours. In that case, simply be patient and check back with your admin if the problem is blocking your work.
Until the fix lands, there’s no official workaround Microsoft has published. If the error is preventing you from completing a specific task, try working around it by using an alternative path — for example, accessing mail through Outlook on the web or the New Outlook — as a temporary measure, though that won’t resolve the underlying issue.
Bottom line: Microsoft is aware of the bug and actively building a fix, but there’s no confirmed release date yet. We’ll update this story as soon as the Outlook Team shares more details.
Source: Neowin
Over to you: Have you hit this error in Classic Outlook, or are you one of the users who hasn’t noticed anything wrong?
