How to Fix Outlook Closes Unexpectedly Issue?
Written By Aaruni Arora 
Updated On November 04, 2026 Written By Aaruni Arora Updated On November 04, 2026 You open Outlook to send an important email to your team, only to find that Outlook keeps closing by itself. Even after launching it again and again, nothing seems to work. This can happen because of a faulty add-in, an outdated Microsoft 365 or Office installation, or a damaged Outlook data file.
This guide covers the top fixes for Outlook 2016, 2019, 2021, 2024, and Microsoft 365 (Classic Outlook), and explains whether the error occurs in New Outlook and how to fix it. Let’s first understand the main reasons behind this error.
There are many reasons for this issue, and we have listed a few of the common ones below:
The methods to resolve the Outlook keeps closing by itself error revolve around simple fixes that can be easily attempted by users. Just make sure that you’ve a backup of your mailbox data and then update your Office 365 to the latest available version.
Note: Methods 1 to 7 below apply to Classic Outlook, meaning Outlook 2016, 2019, 2021, 2024 and the Desktop app in Microsoft 365. They do not apply in the same way to New Outlook for Windows or Outlook on the Web (also known as Outlook Web App). For those, see the New Outlook section later in this article.
Fact: Support for Outlook 2016 and Outlook 2019 ended on October 14, 2025, so they no longer receive security updates. If “update to the latest version” is not possible on your installation, consider moving to Outlook 2021, Outlook 2024 or Microsoft 365.
Antivirus software like McAfee, Avast, Avira, etc., cause issues with Outlook due to specific settings you have set as per your preference or enabled by default.
Try disabling the security software/antivirus tool temporarily and check if it helps or not. Sometimes, the Antivirus can be interfering with Outlook’s functionality and causing it to slow down or stop working. If the issue is fixed, uninstall antivirus quickly to avoid leaving your system unprotected a for long time.
If Outlook keeps shutting down unexpectedly, the first thing you should try is opening it in Safe Mode. This will disable all your add-ins and customizations.
To open Outlook in Safe Mode follow the below steps:
Step 1: Close all instances of Outlook running in the background.
Step 2: Press Win + R on keyboard and type outlook.exe/safe in the Run window.
Step 3: Click Yes when prompted to start in Safe Mode.
Once Outlook is open in Safe Mode, test to see if the issue if fixed or not. If it does, then you know that one of your add-ins or customizations is causing the problem. Many users commonly report that the Kaspersky Anti-Spam add-on was causing the “Outlook closes unexpectedly” problem, and disabling it solved the issue for them.
Follow the steps below to disable Outlook Add-ins:
Step 1: Open Outlook.
Step 2: Click on the File tab, and click Options.
Step 3: From the left pane, click on Add-ins. In the Window on the right-side, make sure COM Add-ins value is selected for Manage. Then, click Go.
Step 4: Deselect all the active Add-in and click OK.
Step 5: Now, close Outlook, restart it, and check if the issues are solved.
If Outlook starts normally, find the incompatible add-in and remove it.
Hardware acceleration is often used by most of the newest applications for Windows. To enhance the overall experience of Outlook, disabling the option of Hardware Acceleration available in the application would come to be a savior.
Follow the steps below to disable the hardware acceleration:
Step 1: Launch Outlook.
Step 2: Go to File > Options.
Step 3: Click Advanced, check Disable Hardware graphics acceleration, and click OK.
Step 4: For the change to take effect, close the application and start Outlook again.
When I was looking for reasons for “Why is my Outlook shutting down unexpectedly”? My answer was a 110 GB OST file that was just too big much for my Outlook to handle. As per Microsoft, modern Outlook supports OST files up to 50 GB. When your OST file size grows bigger than the 50 GB limit, Outlook may hang or crash often. To fix Outlook keeps closing itself, I had to resolve the oversized OST file issue.
Outlook profile corruption is another major reason why your Outlook is closing unexpectedly. To fix Outlook keeps closing itself, you must create a new Outlook profile with these steps:
Step 1: Go to Control Panel > Mail > Show Profiles.
Step 2: Then, click the Add button and configure the new Outlook profile.
Note: Remember to make the new profile your default one by selecting the Always use this profile option.
If Outlook keeps closing by itself even after disabling faulty add-ins and updating the email client to its latest version, you might have some damaged system files. Repairing the Office 365 installation can help with Outlook crashes in some cases. There are two ways by which you can do this: Quick Repair or Online Repair. Here are the steps to repair your Office 365 installation:
Note: Quick Repair and Online Repair are available for Click-to-Run installations. Older MSI-based installations of Office 2016 show a single Repair option.
Corruption in the Outlook data file, be it OST or PST, can also be one of the reasons for Outlook keeps closing by itself. To resolve the issue, you need to repair the data files. To repair OST file, follow these steps:
Step 1: Go to the location where your OST file is. Select it and delete it.
Step 2: Open Outlook. It will connect to Exchange and automatically build a new healthy OST file.
Note: This works for Exchange, Microsoft 365, and IMAP accounts. For POP accounts, your data is stored in a PST file, so do not delete it.
If you are facing crashing issue because of a corrupt PST file, you can use the Inbox Repair Tool to repair your PST file. Inbox Repair Tool (ScanPST.exe) is a free built-in utility developed by Microsoft that’s used to scan and repair corrupt or damaged PST files. It can easily fix minor corruption or structural inconsistencies in the PST file.
Yes, this Outlook keeps closing by itself error occurs in New Outlook for Web too, where the app fails to launch, closes right after opening, or crashes mid-function. This happens mostly because of corrupted cache files or because the Windows 11 update was not installed properly. There is also a known startup failure that has affected ARM-based Windows 11 devices in a recent update, though Windows has released the corresponding fix for it.
New Outlook does not use PST/OST files, COM add-ins or Outlook profiles, so the Classic methods above will not work. Try these fixes instead:
Tip: Check your mailbox in Outlook on the Web: If the mailbox works in the browser, the problem is with the app, not with your account or data.
If Outlook on the Web keeps closing or freezing, refresh the page, clear the browser cache, or update or switch your browser. Safe Mode, add-in, profile, and file repair steps do not apply to the web version.
Hopefully, one of these solutions worked for you in fixing the “Outlook closes unexpectedly” problem. Most of the time, this error is resolved after disabling a faulty add-in or updating Office 365 to the latest version. With the above-mentioned methods, you can fix the Outlook closes unexpectedly issue in Outlook 2016, 2019, 2021, 2024, Microsoft 365 desktop mode, New Outlook for Windows, and Outlook on the Web (also known as Outlook Web App).
If nothing works, then you need to check for corruption in your PST file; maybe that’s causing such problems. Run ScanPST.exe once to see if you can open Outlook normally or not. If ScanPST.exe can’t fix the data file, you can opt for a dedicated Outlook PST repair tool to repair and recover your data.
A: No. OST is basically an offline copy of your mailbox on the Exchange Server. When you delete it, the original data stays safe on the server.
A: OST file’s size limit is different than the size limit of your mailbox. You can change or configure the OST or PST file size limit with the help of Windows Registry settings.
A: Not necessarily. This module shows which file failed at what moment, but it doesn’t state the cause behind the failure. If you need to find it in the Event Viewer, just go to Windows Logs > Application and look for crash Event 1000 or 1001.
A: No, New Outlook for Windows does not use PST/OST files, COM add-ins, or Outlook profiles, so ScanPST.exe, the outlook.exe /safe command, and the new-profile method do not apply. Instead of this, update Windows and the app, then go to Settings > Apps > Installed apps > Outlook (new) > Advanced options and try Repair, then Reset. If it still closes, remove and re-add your account or reinstall the app.
A: Outlook on the Web runs in your browser, so the Classic fixes (Safe Mode, add-ins, profiles, OST/PST repair, and Office repair) do not apply. Refresh the page, clear the browser cache, disable browser extensions, or try another browser or an InPrivate/Incognito window. If your mailbox works there but the desktop app keeps closing, the problem is with the app, not your account or data.