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Outlook Classic was frequently "Not Responding" for the last two days, after Window Update (KB5074109). Now it is not opening and stuck up at "loading profile". Outlook classic is not seen in installed applications, automatically switched to New Outlook, which I don't like to use.
Using Classic Outlook on Windows for personal email, calendar, and contact management
My problem has been solved with assistance of Copilot. I have reinstalled Outlook Classic.
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I too have problems with outlook freezing up before all messages could be loaded. I have not been able to uninstall the last update.
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2026-01-25 - A fix for the KB5074109 Outlook/OneDrive bug has been released as KB5078127.
This seems to be an emerging problem with Outlook after the January KB5074109 Update, that update is affecting Outlook POP accounts, this is being reported by many people after that update, some people have reported if you uninstall the Windows update, that will resolve the problem, also, it is best to open the Feedback Hub app in Windows and report this to the Windows developers, if more people report this, then they will investigate the problem and provide a patch for this problem.
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I too have problems with outlook freezing up before all messages could be loaded. I have not been able to uninstall the last update.
@Jessica Lee @Donald Mewett @Dave Ebertz
If you use Classic Outlook for Windows and have any POP email accounts, this is a know bug:
There are two temporary fixes. Doing either one should fix the issue:
1 -- Move any PST files out of your OneDrive folder and use ScanPST to check for errors.
How to remove an Outlook .pst data file from OneDrive
ScanPST
https://learn.microsoft.com/en-us/troubleshoot/outlook/data-files/how-to-repair-personal-folder-file
Once you have moved all of your PSTs you can resume Windows Updates. KB5074109 won't break your Outlook.
2 -- Uninstall the Jan 2026 Update KB5074109 and Pause Windows Updates.
How to uninstall a Windows Update
Pause Windows Updates
If you can not uninstall KB5074109 thru normal means:
See this Microsoft Learn Q&A thread for alternatives.
Or contact Microsoft Support and ask "How to uninstall KB5074109?"
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And....oops.... I just noticed that my Outlook address book is empty. I used to have hundreds of people in my address book. Looks like some calendar items might be missing too. Can you advise me what to do about this?
@James Haufler said
my Outlook address book is empty ... some calendar items might be missing too
Did you use the "Uninstall KB5074109" or the "Move your PST files" workaround?
If you used the Move PSTs method, have you done a ScanPST on the files once they are out of the OneDrive folder?
ScanPST
https://learn.microsoft.com/en-us/troubleshoot/outlook/data-files/how-to-repair-personal-folder-file
If you used the Uninstall KB5074109 method, then I'm stumped. I would suggest you use the "Ask a question" button at the top of this page to start a new thread specific to your issue. Something like "Outlook PST file missing data after KB5074109 uninstall".
@James Haufler said
my Outlook address book is empty ... some calendar items might be missing too
Contact Microsoft Support directly so they can examine your system.
MS 365 - Admin Only Support
https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-support
MS 365 - User Support
https://www.microsoft.com/en-us/microsoft-365/support
Free Chat Support
https://support.microsoft.com/home/contact
Thanks. I would have used that MS 365 Support, if known earlier. Copilot guided me to uninstall New Outlook and re-install Classic Outlook.
@Nasirud din said
Copilot guided me to uninstall New Outlook and re-install Classic Outlook.
Are you sure you're in the right thread? This one is about problems with existing Classic Outlook for Windows installs that have PST files stored on OneDrive.
Correct, my comment is not relevant to this thread.
I did the "Move PSTs" method. I did not try to do the uninstall the KB5074109 method.
I cannot find the scanpst.exe file anywhere on my computer.
I tried to follow the instructions on the MS website to find the scanpst.exe file but it was nowhere to be found. A search of my entire C: directory yielded nothing.
The MS 365 - User Support link does not work.I am not allowed to use the MS 365 - Admin Only link because I do not have a Business account.
@James Haufler said
I cannot find the scanpst.exe file anywhere on my computer
I have seen reports that it sometimes has a Windows "hidden" flag. Try Windows Explorer -> View -> Show -> Hidden items
The MS 365 - User Support link does not work
Up now for me. Might have been the Microsoft Cloud outage.
I am not allowed to use the MS 365 - Admin Only link because I do not have a Business account.
Yeah. That's how it works.
I tried this: "Windows Explorer -> View -> Show -> Hidden items", but it still did not find scanpst.exe anywhere on my PC.
@James Haufler said
it still did not find scanpst.exe anywhere on my PC.
I am sorry but that's all the advice I can provide. I would suggest you either:
Search the Microsoft Q&A Forum for similar questions. e.g.
https://learn.microsoft.com/en-us/answers/questions/4654966/i-need-help-finding-the-scanpst-exe-file-on-my-win
Contact Microsoft Support so they can examine your PC.
MS 365 User Support https://www.microsoft.com/en-us/microsoft-365/support
Free Chat Support https://support.microsoft.com/home/contact
Use the "Ask a question" button at the top of this page to create a new question specifically for your inability to locate ScanPST.
Thanks. I took my PC into Best Buy. They are very much aware of the troubles that Outlook users have been having since the January update of Windows 11. They were able to quickly fix my problem with the Outlook Address book without running scanpst.exe.