Microsoft Outlook — "Cannot start Microsoft Outlook" — What It Means & How to Fix It

What Does This Error Mean?

This error means Outlook tried to launch but something stopped it from loading properly. The most common culprit is a damaged Outlook profile or a corrupted data file. Outlook shows this message instead of the main window and refuses to open until the problem is fixed.

Affected Models

Microsoft Outlook 2016
Microsoft Outlook 2019
Microsoft Outlook 2021
Microsoft 365 Outlook

Common Causes

The Outlook profile is corrupted or contains incorrect settings
The Outlook data file (.pst or .ost) is damaged
A recently installed add-in is crashing Outlook before it can fully load
The Navigation Pane configuration file is corrupted
Office was recently updated or repaired and something did not complete correctly

How to Fix It

Start Outlook in Safe Mode. Hold the Ctrl key and double-click the Outlook icon. Click Yes when asked if you want to start in Safe Mode.

Safe Mode bypasses add-ins and a damaged Navigation Pane. If Outlook opens in Safe Mode, an add-in or the Navigation Pane is the cause.
If Safe Mode works, disable your add-ins. Go to File > Options > Add-ins. At the bottom, next to Manage, click Go. Uncheck all add-ins and click OK. Restart Outlook normally.

Re-enable add-ins one at a time to find the one causing the crash.
Reset the Navigation Pane. Press Windows + R, type outlook.exe /resetnavpane, and press Enter.

A corrupted Navigation Pane configuration is one of the most common causes of this error. This command resets it without deleting your emails.
Create a new Outlook profile. Go to Control Panel > Mail > Show Profiles > Add. Set up the new profile with your email address and set it as the default.

A fresh profile bypasses any corruption in the old one. Your emails stored on the server will re-download automatically.
Repair the Outlook data file using the ScanPST tool. Search for scanpst.exe on your PC, open it, browse to your .pst or .ost file, and click Start.

ScanPST is a free Microsoft tool built into Office. It finds and repairs errors in your Outlook data file without deleting messages.

When to Call a Professional

If none of the steps below work and you need access to your emails urgently, call your IT support team. For home users, Microsoft's free support chat at support.microsoft.com can walk you through advanced fixes. Data recovery professionals can also extract emails from a corrupted .pst file if needed.

Frequently Asked Questions

Will I lose my emails if I create a new profile?

If your emails are stored on a server (like Microsoft 365, Exchange, Gmail, or IMAP), no — they are safe on the server and will re-download. If you use POP3 and emails are stored only on your PC, you could lose them if you delete the old profile. Do not delete the old profile — just create a new one and set it as default first.

Where is the scanpst.exe file on my computer?

The location depends on your Office version and whether it is 32-bit or 64-bit. For Microsoft 365 64-bit, check: C:\Program Files\Microsoft Office\root\Office16\ For older versions, check: C:\Program Files (x86)\Microsoft Office\Office16\ You can also press Windows + S and search for scanpst.

I see a message about a compatibility mode or incompatible version. What does that mean?

This can happen after a Windows or Office update changes internal settings. The fix is usually to reset your Outlook profile or repair the Office installation. Go to Control Panel > Programs > Microsoft 365 > Change > Quick Repair and let it run.