Outlook Keeps Crashing or Won’t Open: How to Fix It

Outlook crashing is one of the most disruptive things that can happen to a working day. Whether it refuses to open at all, freezes after a few minutes, or crashes the moment you click Send, the cause is usually one of a handful of things — and most of them are fixable without reinstalling Office. Here’s how to work through it systematically.

Start With Safe Mode

The first thing to try is launching Outlook in safe mode. This starts Outlook with add-ins disabled and a minimal configuration, which immediately tells you whether the problem is Outlook itself or something loaded on top of it.

Hold Windows key + R, type the following, and press Enter:

outlook.exe /safe

If Outlook opens cleanly in safe mode, the crash is almost certainly caused by a faulty add-in. If it still crashes, the problem is deeper — skip ahead to the profile or Office repair sections.

Disable Problematic Add-ins

Add-ins are the most common cause of Outlook crashes. Third-party tools like Teams Meeting, Zoom, antivirus plugins, CRM connectors and PDF printers all hook into Outlook at a low level — and any one of them can cause instability, particularly after a Windows or Office update.

1. Open Outlook in safe mode (using the command above)
2. Go to File > Options > Add-ins
3. At the bottom, set the dropdown to COM Add-ins and click Go
4. Uncheck all add-ins and click OK
5. Restart Outlook normally

If it stops crashing, re-enable add-ins one at a time — restarting after each — until you find the culprit. Once identified, either leave it disabled, update it, or contact the vendor for a fix.

Repair Your Office Installation

If safe mode doesn’t help and disabling add-ins makes no difference, the Office installation itself may be corrupted. This can happen after Windows updates, failed Office updates, or storage errors. The built-in repair tool fixes this without touching your data.

1. Press Windows key + I to open Settings
2. Go to Apps > Installed Apps (or Apps & Features on Windows 10)
3. Find Microsoft 365 or Microsoft Office in the list
4. Click the three dots and select Modify
5. Choose Quick Repair first — this runs offline and takes a few minutes
6. If the issue persists after a restart, run Online Repair — this reinstalls Office files from Microsoft’s servers

Online Repair is more thorough but takes longer and requires a reasonable internet connection. It won’t remove your account settings or email data.

Recreate Your Outlook Profile

Your Outlook profile holds your account configuration, cached settings, and various preferences. If it becomes corrupted — which can happen after a failed update, a sync error, or an abrupt shutdown — Outlook may crash on startup every time.

1. Close Outlook completely
2. Open the Control Panel (search for it in the Start menu)
3. Go to Mail (Microsoft Outlook)
4. Click Show Profiles
5. Click Add and create a new profile with a name like “Outlook New”
6. Set it to prompt for a profile on startup, then open Outlook and select the new profile
7. Re-add your email account

If Outlook runs cleanly with the new profile, your old one was the problem. You can delete it once you’re satisfied the new one is working correctly.

Fix a Corrupted OST File

For Microsoft 365 and Exchange accounts, Outlook stores a local cache of your mailbox in an OST file. If this file is corrupted — due to a crash mid-sync, a full disk, or storage errors — Outlook may fail to open or hang on the loading screen.

1. Close Outlook
2. Navigate to C:Users[YourName]AppDataLocalMicrosoftOutlook
3. Find the file ending in .ost — it will be named after your email address
4. Rename it (add .old to the end) rather than deleting it immediately
5. Reopen Outlook — it will create a fresh OST file and re-sync from the server

The re-sync will take time depending on your mailbox size. Once complete, delete the renamed .old file to free up disk space.

Run the Inbox Repair Tool (SCANPST)

If you use a POP3 or IMAP account with a local PST file rather than Exchange, use the built-in Inbox Repair Tool instead:

1. Find SCANPST.EXE — it’s usually in C:Program FilesMicrosoft OfficerootOffice16
2. Run it and browse to your PST file
3. Click Start — it will scan and report errors
4. Click Repair if issues are found

New Outlook vs Classic Outlook

If you’re using the new Outlook (the one that looks more like Outlook.com and arrived as a toggle in Windows 11), the troubleshooting steps above mostly apply to classic Outlook. The new Outlook is a web-wrapped app and behaves differently.

For the new Outlook specifically:

• Try signing out completely and back in via Settings > Accounts
• Clear the app cache: open Run (Win + R), type %localappdata%PackagesMicrosoft.OutlookForWindows_8wekyb3d8bbweLocalCache and delete the contents
• If it won’t open at all, use Windows Settings to repair or reset the app under Apps > Installed Apps > Microsoft Outlook > Advanced Options

If you’re on Windows 11 and find the new Outlook unreliable, you can switch back to classic Outlook using the toggle in the top-right corner — at least for now while Microsoft continues to develop it.

Check for Windows Compatibility Issues

Less commonly, Outlook crashes can be triggered by a recent Windows update that introduced a conflict. Check Windows Update history to see if a new update landed around the time the crashes started. If so:

• Check the Microsoft Outlook known issues page to see if it’s a recognised problem with a fix or workaround
• Run Windows Update again — sometimes the fix comes through as a subsequent update within days
• Check the Windows Event Viewer (Win + R, type eventvwr) under Windows Logs > Application for crash entries that may point to a specific DLL or process

When Nothing Works

If you’ve worked through every step above and Outlook still crashes, it’s worth considering a full uninstall and reinstall via the Microsoft Support and Recovery Assistant (SaRA tool). This handles stubborn Office installations that the standard uninstaller leaves behind.

Also worth checking: available disk space. Outlook needs room to work — if your C: drive is nearly full, crashes and freezes are a common symptom. Clear some space and retest.

Outlook crashes are frustrating, but they’re rarely permanent. Work through these steps methodically and you’ll almost always find the cause without needing to call IT support.

For a full index of every Outlook guide and troubleshooting fix on Serverman, see the Microsoft Outlook complete guide and troubleshooting hub.