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Outlook fix | Windows | classic & new Outlook

Outlook opens then closes immediately? Here's why, and the fix

When Outlook opens then closes immediately, or crashes as soon as you open it, the cause is almost always one thing running at start-up: a faulty add-in, a damaged data file, or a corrupt profile. Start Outlook in Safe Mode first, because if it stays open that tells you exactly where to look. Below is the plain-English, step-by-step fix for both classic and new Outlook on Windows, and if you would rather not touch it, we will fix it for you remotely, usually in minutes. Rated 4.9 on Google.

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  • ● Windows only
  • ● Classic & New Outlook
  • ● Safe Mode first

Answer first

The quick answer: start Outlook in Safe Mode

If Outlook opens then closes immediately, the fastest way to find the culprit is to launch it in Safe Mode, which loads Outlook without any add-ins.

  1. Close Outlook completely.
  2. Press the Windows key + R to open the Run box.
  3. Type outlook.exe /safe (there is a space before the slash) and press OK.

If Outlook stays open in Safe Mode, an add-in is crashing it — jump to the add-in fix below. If it still closes even in Safe Mode, the problem is the data file or profile — go to the repair and profile steps. This one test tells you which half of the guide you need, so you don't waste time.

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The real fixes

Step-by-step fixes for classic Outlook

1. Disable the faulty add-in (the most common cause). With Outlook open in Safe Mode, go to File > Options > Add-ins. At the bottom, next to Manage, choose COM Add-ins and click Go. Untick every add-in, click OK, then close and reopen Outlook normally. If it now stays open, re-enable the add-ins one at a time (reopening Outlook after each) until it crashes again — that last one is the offender. Leave it disabled or check for an update.

2. Watch out for the Teams Meeting Add-in crash. Since 12 March 2026, older classic Outlook builds (Version 2402, Build 17328.20142 or lower) can crash on launch because of a clash between the newest Teams Meeting Add-in and an older Windows file (MSVCP140.dll) bundled with those Office builds. If that is you, the real fix is to update Office: because Outlook won't open, open Word instead and go to File > Account > Update Options > Update Now. As a temporary workaround you can untick the Microsoft Teams Meeting Add-in for Microsoft Office via the Safe Mode add-ins steps above. Microsoft has also shipped a Teams-side fix, so keeping both Office and Teams up to date resolves it.

3. Repair Office. If no add-in is to blame, run an Office repair. Close all Office apps, then go to Settings > Apps > Installed apps, find Microsoft 365 (or Office), click the three dots and choose Modify, then Quick Repair. If that doesn't help, run Online Repair (this needs an internet connection and takes longer). Your emails are not touched by this.

4. Repair the data file with scanpst.exe. A corrupt Outlook data file can crash it on open. Close Outlook and run the built-in Inbox Repair Tool, scanpst.exe, usually found in C:\Program Files\Microsoft Office\root\Office16. Browse to your .pst or .ost file, click Start, and let it repair. This is safe — it fixes the file in place.

5. Create a new Outlook profile. If the profile itself is damaged, a fresh one often cures the crash. Close Outlook, open Control Panel > Mail (Microsoft Outlook) > Show Profiles > Add, create a new profile, add your account, and set it as the default. For IMAP, Exchange and Microsoft 365 accounts your mail re-downloads from the server, so nothing is lost — but if you have any POP account, back up your .pst file first, because POP mail lives only on your PC.

6. Check your antivirus isn't quarantining Outlook. Occasionally security software wrongly flags Outlook and blocks it from staying open. Open your antivirus, check its quarantine and protection history, and add Outlook (outlook.exe) as an exception if it has been blocked.

New Outlook

Fix for the new Outlook app

The new Outlook doesn't use add-ins or profiles in the same way, so if new Outlook opens then closes immediately, reset its local cache and sign-in files:

  1. Close new Outlook (check no olk.exe is still running in Task Manager).
  2. Press Windows key + R, type %localappdata%\Microsoft and press Enter.
  3. Find the folders named Olk and OneAuth.
  4. Right-click each and choose Rename — add .bak to the end (so they become Olk.bak and OneAuth.bak).
  5. Start new Outlook again and sign back in when prompted (you may be asked to complete MFA again).

These two folders only hold temporary cache and cached sign-in tokens — not your actual emails, which live safely on Microsoft's servers — so renaming them is reversible and nothing is lost. If it works, you can delete the .bak folders later. If new Outlook still won't stay open, it is quicker to let us take a look than to keep fighting it.

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Frequently asked

Why does Outlook open then close immediately?

In the vast majority of cases something loads at start-up and crashes Outlook: a faulty add-in (very common), a corrupt Outlook data file (.pst/.ost), or a damaged profile. Starting Outlook with outlook.exe /safe skips add-ins — if it then stays open, an add-in is your culprit; if it still closes, look at the data file and profile.

How do I open Outlook in Safe Mode?

Close Outlook, press Windows key + R, type outlook.exe /safe (with a space before the slash) and click OK. Safe Mode loads Outlook without any add-ins, so it's the quickest way to tell whether an add-in is causing the crash.

Outlook crashes as soon as I open it since March 2026 — is that a known bug?

Yes. Older classic Outlook builds (Version 2402 / Build 17328.20142 or lower) started crashing on launch from 12 March 2026, due to a clash between the newest Teams Meeting Add-in and an older Windows file (MSVCP140.dll). The fix is to update Office (open Word, then File > Account > Update Options > Update Now) or untick the Microsoft Teams Meeting Add-in via Safe Mode. Keeping Teams updated also resolves it.

Will I lose my emails if I create a new profile or run scanpst?

scanpst.exe repairs your data file in place and doesn't delete mail. For Microsoft 365, Exchange and IMAP accounts, a new profile re-downloads everything from the server, so nothing is lost. The only account type where mail lives solely on your PC is POP — back up your .pst file before touching the profile if you use POP.

The new Outlook app closes the moment it opens — what do I do?

Close new Outlook, press Windows key + R, type %localappdata%\Microsoft, and rename the Olk and OneAuth folders (add .bak to each). Restart new Outlook and sign in. These folders only hold cache and cached logins, not your emails, so it's safe and reversible.

Can 365 Techies fix this remotely?

Yes. We connect securely with Splashtop SOS while you watch, phone you first before starting, and access ends the moment it's fixed. Most Outlook-won't-open crashes are sorted in minutes, same day. Call 01202 775566.

Outlook still closing the second it opens?

Call 365 Techies on 01202 775566. We watch, we phone you first, and access ends the moment it's fixed. Same-day, usually sorted in minutes.

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