Outlook won't open because of a corrupted profile, a conflicting add-in, an outdated version, or a Windows update that broke compatibility
When Outlook refuses to launch, the cause is usually one of four things: the program file itself is damaged, an add-in you installed is blocking startup, your Windows system is out of date, or your Outlook profile — the file that stores your account settings and cached mail — has become corrupted. Most of these have straightforward fixes you can try in order, starting with the fastest.
Before you do anything else, restart your computer. This clears temporary memory problems and often solves the issue without further steps. If Outlook still won't open after a restart, move to the next section.
Key Takeaways
- Restart your computer first — this solves the problem roughly half the time and takes two minutes.
- Launch Outlook in Safe Mode to test whether an add-in is blocking it; if it opens in Safe Mode, disable add-ins one at a time until you find the culprit.
- Check Windows Update and install any pending updates, since Outlook often breaks after a Windows patch until both are current.
- Repair Outlook through the Control Panel (Windows) or Applications folder (Mac) if Safe Mode and updates do not work.
- As a last resort, create a new Outlook profile, which forces the program to rebuild its settings file from scratch.
Start Outlook in Safe Mode to rule out add-ins
Add-ins are small programs that extend Outlook's features — things like calendar connectors, email security tools, or CRM integrations. A broken or outdated add-in can prevent Outlook from opening at all. Safe Mode launches Outlook without loading any add-ins, so if it opens in Safe Mode, you know an add-in is the problem.
On Windows: Hold down the Ctrl key and double-click the Outlook icon, or open the Run dialog (Windows key + R), type outlook.exe /safe, and press Enter. Outlook will launch with a message saying it is running in Safe Mode.
On Mac: Hold down the Shift key while opening Outlook from the Applications folder. You will see a dialog asking whether to disable add-ins; click Continue.
If Outlook opens in Safe Mode, an add-in is blocking it. Close Outlook, restart normally, and then disable add-ins one at a time until you find which one is causing the problem. In Outlook, go to File > Options > Trust Center > Trust Center Settings > Disabled Items (Windows), or Outlook > Preferences > General > Manage Add-ins (Mac). Uncheck each add-in, restart Outlook, and test. When Outlook opens without crashing, you have found the problem add-in — either update it or remove it permanently.
Check for Windows and Outlook updates
Microsoft releases updates to both Windows and Outlook regularly. When one updates but the other does not, they can conflict and prevent Outlook from launching. Checking for updates is fast and often solves the problem.
On Windows: Open Settings, go to Update & Security (or System > Windows Update on newer versions), and click Check for updates. Install any updates shown, then restart your computer. After the restart, open Outlook again.
If you use Outlook as part of Microsoft 365 (the subscription version), it updates automatically, but you can force a check: open any Microsoft 365 app, go to File > Account, and look for an Update Options button. Click it and select Update Now.
On Mac: Open the App Store, click Updates in the top right, and install any updates for Outlook or macOS. Restart your Mac afterward.
Repair Outlook through the Control Panel or Applications
Outlook has a built-in repair function that can fix corrupted program files without uninstalling and reinstalling the whole process. This is faster than a full reinstall and usually preserves your settings.
On Windows: Open the Control Panel, go to Programs > Programs and Features, find Microsoft Office or Microsoft 365 in the list, click it, and then click Change. A dialog will appear with two repair options: Quick Repair (fixes obvious problems in minutes) and Online Repair (downloads fresh program files from Microsoft, takes longer but fixes deeper corruption). Start with Quick Repair. If Outlook still will not open, run Online Repair.
On Mac: Open Finder, go to Applications, right-click Microsoft Outlook, and select Move to Trash. Then go to Applications > Utilities, open Terminal, and paste this line: /Library/process\ Support/Microsoft/Office/RemoveOfficeFiles.sh. Press Enter. This removes corrupted settings files. Then reinstall Outlook from the App Store or Microsoft's website.
Create a new Outlook profile
Your Outlook profile is a folder on your computer that stores your account settings, passwords, and cached mail. If this file becomes corrupted, Outlook may refuse to open. Creating a new profile forces Outlook to build a fresh settings file from scratch. You will need to re-enter your email account information, but your mail on the server will still be there.
On Windows: Open the Control Panel, go to Mail (or search for "Mail" in the Control Panel). Click Show Profiles, then Add. Give the new profile a name (like "Outlook New"), click OK, and follow the prompts to enter your email address and password. Once created, go back to the Mail dialog, select the new profile, and click Set as Default. Close the dialog and try opening Outlook.
On Mac: Quit Outlook completely. Open Finder, press Command + Shift + G, paste ~/Library/Group Containers/UBF8T346G9.Office/, and press Enter. Look for a folder named something like Outlook 16 Profiles or com.microsoft.Outlook. Rename it by adding ".old" to the end (for example, Outlook 16 Profiles.old). This hides the old profile without deleting it. Open Outlook; it will create a new profile automatically. Enter your email account information when prompted.
Uninstall and reinstall Outlook if nothing else works
If Outlook still will not open after trying Safe Mode, updates, repair, and a new profile, the program files are likely too corrupted to fix. A full uninstall and reinstall is the last reliable option.
On Windows: Open the Control Panel, go to Programs > Programs and Features, find Microsoft Office or Microsoft 365, click it, and select Uninstall. Follow the prompts to remove it completely. Restart your computer, then reinstall Outlook from the Microsoft 365 website (if you have a subscription) or from the Office installation media you originally used.
On Mac: Open Finder, go to Applications, drag Microsoft Outlook to the Trash, and empty the Trash. Then go to Applications > Utilities, open Terminal, and run /Library/process\ Support/Microsoft/Office/RemoveOfficeFiles.sh to clean up leftover files. Restart your Mac and reinstall Outlook from the App Store or Microsoft's website.
Frequently Asked Questions
Does Outlook have to be closed before I try Safe Mode?
Yes. If Outlook is already running, close it completely first. You can check the taskbar (Windows) or Activity Monitor (Mac) to make sure no Outlook process is still running in the background. Then use the Safe Mode command.
Will creating a new profile delete my emails?
No. Your emails are stored on the mail server, not in the profile. When you add your account to the new profile and sign in, Outlook will read your mail again. You may lose cached copies of very old emails if you had not synced them, but nothing is permanently deleted.
What if Outlook opens but then crashes when ready?
This usually means an add-in is crashing after startup rather than blocking it. Try Safe Mode first to confirm. If Outlook stays open in Safe Mode, disable add-ins as described in the Safe Mode section. If it crashes even in Safe Mode, run the Online Repair option.
Can I use webmail while I fix Outlook?
Yes. Go to outlook.com or outlook.live.com, sign in with your email address and password, and you can read and send mail from any browser while you troubleshoot the desktop app. This does not interfere with fixing Outlook.
How long does Online Repair take?
Online Repair usually takes 10 to 30 minutes depending on your internet speed and how much of Outlook needs to be downloaded. Do not interrupt it or restart your computer while it is running.