Why Outlook closes immediately after starting and how to fix the problem

On July 15, 2020, the Outlook app, part of the Microsoft Office suite, started closing immediately after launch, with error code 0xc0000005. Users around the world were affected during those 24 hours, and the problem was reported globally on specialist forums.

Users who checked the application logs in the operating system could see that OUTLOOK.EXE had closed with exception code 0xc0000005. More precisely, the error could look similar to the one below.

Faulting application name: OUTLOOK.EXE, version: 16.0.13001.20266, time stamp: 0x5ef262ee
Faulting module name: mso98win32client.dll, version: 0.0.0.0, time stamp: 0x5ef2aa2d
Exception code: 0xc0000005
Fault offset: 0x000474b2
Faulting process id: 0x4cf0
Faulting application start time: 0x01d65ac9b0e13874
Faulting application path: C:\Program Files (x86)\Microsoft Office\root\Office16\OUTLOOK.EXE
Faulting module path: C:\Program Files (x86)\Common Files\Microsoft Shared\Office16\mso98win32client.dll
Report Id: 908e152f-636f-4f5a-9717-48a5576b3ccd
Faulting package full name:
Faulting package-relative application ID:

At the time, the Microsoft 365 team confirmed in a post on Twitter (now X) that the problem was caused by an update and was being investigated.

As a temporary workaround, Microsoft advised users to use Outlook in a web browser or the mobile app until the error was fixed. Microsoft published a fix the same day; it reached users over the following hours, and Outlook picked it up automatically on restart.

Other workarounds for the Outlook app closing immediately after launch

Solution 1: roll back to the June 2020 version of the Office suite

1. Open Command Prompt with administrator rights.
2. Change the working directory with the command cd “\Program Files\Common Files\microsoft shared\ClickToRun”, then press Enter.
3. Once you’re in the ClickToRun folder, run the following command: officec2rclient.exe /update user updatetoversion=16.0.12827.20470, then press Enter.
4. The Microsoft Office suite will then download the specified version, 16.0.12827.20470. Depending on the speed of your internet connection, this step can take anywhere from a few minutes to tens of minutes.
5. Once the message Updates were installed appears on screen, you can close the window.
6. Outlook should now work properly, but if it doesn’t, go back to step 2 and use the command officec2rclient.exe /update user updatetoversion=16.0.12527.20880.

The version numbers above were the right ones for the July 2020 error; today, those versions are old and no longer receive security updates. If a new update breaks Outlook, pick the previous version from Microsoft’s Microsoft 365 Apps update history page. After rolling back, temporarily turn off updates (in Outlook: File > Office Account > Update Options > Disable Updates); otherwise, Office will update itself back to the faulty version. Turn updates back on as soon as Microsoft publishes a fix.

Solution 2: start Outlook in Safe Mode

1. Hold down the Ctrl key, then start the Outlook app.
2. A window will ask whether you want to start Outlook in Safe Mode.
3. Select Yes.

What to keep in mind about Safe Mode: Outlook will start without add-ins, including security add-ins, because they’ll be disabled. Use this method if you want a quick fix. What’s more, you’ll need to repeat the procedure every time you start Outlook, at least until Microsoft releases the fix.

Why does Outlook still close immediately after starting in 2026?

Most often, because of a faulty add-in, a damaged Outlook data file (PST or OST), a corrupted email profile or a problematic Office update. Error 0xc0000005 actually means the program tried to access an area of memory it didn’t have access to, so it can have several causes, not just the July 2020 bug.

What do you do, step by step, when Outlook closes on startup?

1. Start Outlook in Safe Mode (Ctrl + click on Outlook, or the command outlook.exe /safe in the Run window, which you open with Windows + R). If it works in Safe Mode, the problem is almost certainly an add-in: in File > Options > Add-ins, next to Manage: COM Add-ins, click Go and disable the add-ins one by one until you find the culprit.
2. Update Office from File > Office Account > Update Options > Update Now. Many errors are fixed in newer versions.
3. Repair Office from Windows Settings (Apps > Installed apps): choose Microsoft 365 or Office, then Modify. Start with Quick Repair; if that doesn’t help, use Online Repair.
4. Check the data file. A damaged PST file can be repaired with the Inbox Repair Tool (SCANPST.EXE), which is installed with Office. For Microsoft 365 or Exchange accounts, you can delete the OST file while Outlook is closed: Outlook recreates it on startup, with the data from the server.
5. Create a new profile from Control Panel > Mail (Microsoft Outlook) > Show Profiles > Add, then set it as the default profile.
6. If the problem appeared right after an update, roll back to the previous version, as in Solution 1, and check whether Microsoft has announced a known issue.

Until the problem is fixed, you can work in Outlook on the web or in the Outlook app on your phone, exactly as Microsoft recommended in 2020.

Is classic Outlook still worth it, or should we switch to the new Outlook?

Microsoft launched the new Outlook for Windows in 2024 and is gradually moving users to it, but it has announced that classic Outlook will remain supported until at least 2029. The new Outlook doesn’t use COM add-ins, which cause many of the startup crashes, but some features of classic Outlook are still missing or work differently. It’s worth testing it with a few users first.

If your company still uses Office 2016 or Office 2019, keep in mind that their support ended on October 14, 2025: they no longer receive security updates, and new problems no longer get fixed. You’ll find details about the risks of out-of-support software in the article on the problem with end-of-life (EOL) technology.

If Outlook keeps closing or email problems keep coming back in your company, the RezolvIT helpdesk team can help you remotely: we answer the phone within 15 minutes, and we step in remotely within one hour.