Classic Outlook Crashes When Opening ucrtbase.dll on Windows
Recently many Microsoft 365 users complained that their classic Outlook crashes when opening ucrtbase.dll via faulting module.
This problem starts to occur right after users update to Version 2407 Build 17830.20138
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What makes this crash especially problematic is that none of the traditional fixes like Restarting it, running Outlook in safe mode, or reinstalling the app seem to work. Even highly technical update build reversal failed to fix the issue.
Moreover, the crashes often happen so fast that users cannot even submit an issue ticket. Delaying the official response.
Root cause analysis has revealed that the server-level rule on the Microsoft email account is the primary reason for this issue. Due to corruption, Outlook is unable to process the request and closes randomly.
As the problem is under investigation Microsoft is yet to deploy a complete fix. However, this does not mean that we don’t have some temporary workarounds that can get back the Outlook functionality on your device.
First, let us see what were main objective of the new update it will help us understand what went wrong in its rollout.
How Outlook August 2024 Update Causes Abrupt App Closures
As per the Microsoft release notes the update seems to fix the following user-side complains
- Email category invisible until mail window closes.
- Co-Pilot shows wrong non-Latin character sets.
- Added admin-controlled policy for MailTips that sends alerts to users when emails are blocked, restricted, or contain sensitive information.
There have been other errors in Outlook like when the underlying PST files becomes too large or Autodiscover stops working all of a sudden. These were largely individual level rather than the current one which has spread on a mass scale.
Although these updates aim to improve Outlook’s functionality, these in turn may introduce new issues that could lead to Outlook crashes when opening ucrtbase.dll. Even after thorough testing, it is impossible to replicate every user environment so some edge cases are missed. The recent changes in the update on how Outlook handles UI updates, text rendering on Copiolot, or policy enforcement changes are possible causes for abrupt app closures.
Apart from these functionality updates the latest changes also aimed to address the Microsoft Outlook Remote Code Execution Vulnerability. Researchers submitted their findings on a security vulnerability that exists in MS-Outlook 2016 32/64-bit edition that could allow arbitrary code to run when a maliciously modified file is opened.
To protect users from this issue Microsoft added fixes within the newest update of the Outlook app. Problems in security checks may incorrectly identify server-side rules as external agents leading to an unexpected shutdown.
Let us now head over to the strategies that have worked to fix these issues.
Stop Outlook Crashes when Opening ucrtbase.dll with Default Repair
- Right-click on the Start box in the taskbar.
- Click on Apps and Features
- Find Outlook and select Modify
- The Next step depends on how you installed the App
Click-to-run:
- Select “Online Repair” > “Repair” to fix all issues.
MSI-based:
- Select “Repair” > “Continue” in “Change your installation”.
Then you must follow the instructions that appear on-screen in that order. If for some reason the repair fails to bring Outlook back in working condition then you might have to uninstall and reinstall the application.
Prevent Outlook from Closing Randomly
The specific nature of the problem means that a New clean profile that has yet to receive an o365 account continues to work.
It still works unless the user tries to restart Outlook. The crashing issue begins again. The issue seems to occur only in pure cloud-based accounts as the local on-premise accounts worked without issue.
Check the Event Viewer
- Press Windows + X keys togeter and choose Event_Viewer from the context menu
- Inside the Event Viewer > Go to Windows Logs > Expand Application
- If you see a Faulting module version 16.0.4288.1000 it is an indication of old MSI language.
- To fix it Press Windows + I > Go to Apps > Select Installed Apps > Uninstall old Office language installation.
- Reinstall the latest language accessory pack for Microsoft 365.
However, the most reliable approach to fixing the crash is to do away with all rules set on your Outlook account.
Step by Step Instructions on How to Disable Rules in Outlook
- Step 1. Press the Windows + R keys together to launch the Run module.
- Step 2. Copy Outlook.exe /cleanrules and paste it in the Blank space next to open.
- Step 3. Click OK
Source: Microsoft
Note: If this procedure does not work for you then you need to perform manual rule removal on the Outlook Web Portal.
Once you get your Outlook up and running, we recommend that you should not waste any time and create a backup of all important data present in your account.
How to Keep Outlook Information Accessible After Crash?
Use SysTools Office 365 Backup tool to keep an offline copy of all emails in an easy-to-access manner. Store the data in PST, MBOX, or EML. View it in other email clients if you face errors like Outlook crashes when opening ucrtbase.dll.
Use a date filter, user selection panel, and priority marking to perform a precise selection of all email contact, and calendar data associated with your Outlook account.
Conclusion
In this write-up, users got solutions on what to do if Outlook crashes when opening ucrtbase.dll from the faulting module. Here we explained due to the novel nature of the problem traditional fixes fail to work. As a result, users have to rely on a special instruction set that aims to revoke the server rules.
Which is the main cause of this issue. Moreover, as a suggestion, we recommend users to backup their important Outlook conversations as a safety net against such issues in the future. For that, the best way would be to rely on a professional backup solution.
Frequently Asked Questions
Will Outlook crash on my Mac Device if I install the update?
As of yet, the problem seems to be limited to Windows machines. However, as a precautionary measure, we recommend waiting for the official update from Microsoft before updating the application.
Does the crash affect incoming/outgoing email messages sent via/received on Outlook Client?
As the error occurs on server-side rules there can be an impact on message retrieval in some cases. The Outlook app crashes before you can view the messages or perform any additional step you continue to receive messages that can be accessed via the web app.
Is Outlook Classic support ending?
Microsoft will no longer drop any more updates for the Outlook 2016 version from October 14, 2025 onwards. So it’s recommended to switch to the cloud-based alternative before that.
