Outlook Classic not opening properly or recording sent mails after 2026-01 Security Update (KB5074109) (26200.7623)

Chris Seagrave 350 Reputation points
2026-01-14T12:20:57.8233333+00:00

Hi,

I installed in the Windows Security update (KB5074109) (26200.7623) on 14th January 2026 and following this update Outlook Classic has a couple of problems.

The first is that when I first start my laptop Outlook Classic opens, but when I close it down I am now unable able to open it again as Office tells me it is still open. I can go into Task Manager and close the Background Process relating to Outlook Classic which allows me to open Outlook Classic again, but this is not ideal as I would rather not do this. Alternatively I can restart my laptop and Outlook Classic will open, but if I close it down it won't re-open unless I either close the Outlook Background Process in Task Manager or restart the laptop.

The second issue is that I can send an email and it will be sent to the person I am sending the email to, but it doesn't show as being sent in the Sent Items folder, this is very strange, receiving emails is fine so far.

I have encountered this using a Yahoo Pop account, so I need some guidance on what I can do to resolve these issues in Outlook Classic?

Is there a specific fix in Outlook Classic or do I need to uninstall this (KB5074109) (26200.7623) update?

I can't seem to find a way of uninstalling update (KB5074109) (26200.7623), so may need some guidance here?

Many Thanks,

Chris

Outlook | Windows | Classic Outlook for Windows | For home

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Answer accepted by question author
Suncoast Information Systems 315 Reputation points
2026-01-15T14:58:38.0166667+00:00

Uninstalling KB5074109 worked for us on several PCs

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Answer recommended by moderator
Hornblower409 16,050 Reputation points
2026-01-25T03:29:40.27+00:00

January 24, 2026 - KB5078127 (OS Builds 26200.7628 and 26100.7628) Out-of-band
Fix for Outlook/OneDrive Issues.

https://support.microsoft.com/en-us/topic/january-24-2026-kb5078127-os-builds-26200-7628-and-26100-7628-out-of-band-cf5777f6-bb4e-4adb-b9cd-2b64df577491

I have installed KB5078127 and (so far) I am not seeing any problems.

Just resume your Windows Updates, check for updates, and it should offer you KB5078127.

As I understand it, you do not need to re-install KB5074109 if you previously removed it.

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  1. AI answer

    2026-01-14T12:21:41.68+00:00

    It appears that the issues you are experiencing with Outlook Classic after the January 2026 security update (KB5074109) may be related to known problems that can occur after updates. Here are some steps you can take to troubleshoot and potentially resolve these issues:

    1. Check for Additional Updates: Ensure that you have installed all available updates for Outlook and Windows. Sometimes subsequent updates can fix issues introduced by previous ones.
    2. Repair Outlook: You can try repairing your Office installation. To do this, go to Control Panel > Programs > Programs and Features, select Microsoft Office, and then choose the Repair option.
    3. Disable Add-ins: Sometimes, add-ins can cause Outlook to behave unexpectedly. You can start Outlook in safe mode (hold down the Ctrl key while starting Outlook) to see if it opens without issues. If it does, consider disabling add-ins one by one to identify the culprit.
    4. Check Email Account Settings: Since you mentioned using a Yahoo POP account, ensure that your account settings are correctly configured. Verify that the settings for saving sent items are enabled in your account configuration.
    5. Uninstall the Update: If the above steps do not resolve the issue, you may consider uninstalling the update. To do this, go to Control Panel > Programs > Programs and Features, select View installed updates, find the KB5074109 update, and choose to uninstall it.
    6. Contact Support: If the problem persists, consider reaching out to Microsoft Support for further assistance, especially if the issues are directly related to the update.

    These steps should help you troubleshoot the problems with Outlook Classic. If you need more specific guidance on any of the steps, feel free to ask!

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. Noel Macadangdang 16,895 Reputation points Independent Advisor
    2026-01-14T14:31:54.5166667+00:00

    Hi,

    Thank you for sharing your question. It’s understandably frustrating when Outlook Classic doesn’t reopen properly and your sent messages fail to appear in Sent Items, especially when you’ve confirmed they’re delivered successfully.

    These behaviors appear to stem from how the update affected Outlook’s shutdown process and sent-mail handling. While there isn’t a specific hotfix released yet, here are some steps aligned with Microsoft’s guidance:

    Resolving the "Outlook is still open" message:

    Until an update is released to address this behavior, a viable workaround is to fully close any residual Outlook background processes before reopening the app or simply restart your device. A more lasting solution would be to repair your Office install, or rename the Outlook registry profile folder, which often resolves stuck background tasks.

    Ensuring mails are saved in Sent Items

    This is a common setting oversight or result of corrupted profile settings after updates. To verify:

    Go to File → Options → Mail, and ensure the option “Save copies of messages in the Sent Items folder” is checked.

    If it’s already enabled, the next step is to repair or recreate your Outlook profile—Microsoft reports this fixes many mail-sync issues.

    Uninstalling the KB5074109 update (if needed):

    If you prefer to remove the update temporarily, follow these steps:

    Open Settings → Windows Update → Update history → Uninstall updates, locate KB5074109, and choose Uninstall, then restart your PC.

    I hope this helps.

    Best Regards,

    Noel

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  3. Hornblower409 16,050 Reputation points
    2026-01-15T05:07:23.3066667+00:00

    How to uninstall KB5074109

    These instructions are for Advanced Users Only. If you do not fully understand what is being done here, do not proceed.

    KB5074109 is a combined package containing a Servicing Stack Update (SSU), so it cannot be uninstalled using the standard "Uninstall updates".

    1 -- Open a Command Prompt as administrator.

    2 -- Run the command:
    dism /online /get-packages /format:table

    3 -- Look at the bottom of the output for the line:
    Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.7623.1.20 | Installed | Security Update | 2026-01-14

    It might also be: Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.7623.1.10 , if so, use that value in the next command.

    4 -- Run the command:
    dism /online /remove-package /PackageName:Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.7623.1.20

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