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Classic Outlook · Windows

"Cannot open the Outlook window" — the /resetnavpane fix

That "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened" message usually means the tiny file storing your navigation-pane layout has become corrupt. Press Windows key + R, type outlook.exe /resetnavpane and press Enter — it rebuilds that file and normally lets Outlook open straight away, without touching a single email.

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By the 365 Techies team · Reviewed 10 October 2026

Why it happens

What "cannot open the Outlook window" actually means

This is a classic Outlook for Windows error (the older desktop app with the ribbon and your folders down the left-hand side — not the New Outlook). When Outlook starts it reads a small settings file that remembers your navigation pane: which folders are pinned, the order of your accounts, your favourites and shortcuts. If that file gets corrupted — often after a crash, a forced shutdown, a OneDrive hiccup or a botched update — Outlook can't make sense of it and refuses to open, throwing "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened."

The good news: this is a layout file, not your mail. Your emails, calendar and contacts live safely in your data file (or on the server). Rebuilding the navigation file fixes the error without losing anything, so you can work through the steps below with confidence.

// WINDOWS PCS ONLY

We do not support Outlook on Apple Macs, iPads or iPhones. Apple does not allow our remote-support tool to take control of an iPad or iPhone (an Apple restriction), and our remote support covers Windows PCs only. On an Apple device, Microsoft’s own Outlook help is the place to start.

// FIX IT WITH ME · STEP BY STEP

Fix it with me, one step at a time

The steps from this guide, one at a time, in the order that fixes the most cases fastest. Tell it what happened and it shows the next step. Nothing here leaves your device.Last reviewed 10 October 2026

Checking which Windows you have…STEP 1 OF 5
  1. 01Rebuild the navigation pane

    Close Outlook. Press Windows key + R, type outlook.exe /resetnavpane and press Enter to rebuild the corrupt navigation-pane file. Your emails are not affected.

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Outlook still won’t open? Our free Techies One Mail is a separate, simpler email program for Windows PCs that can show the email kept with your provider, though it won’t repair Outlook or open its .pst files.

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The fix

Step-by-step: get classic Outlook opening again

  1. Rebuild the navigation pane. Close Outlook completely. Press Windows key + R to open the Run box, type outlook.exe /resetnavpane (one space before the slash) and press Enter. This wipes and rebuilds the corrupt layout file. Often, that's enough for Outlook to open.
  2. If that didn't help, start in Safe Mode. Press Windows key + R again and run outlook.exe /safe. Safe Mode loads Outlook with add-ins switched off. If it opens now, a faulty add-in is the culprit — go to File > Options > Add-ins > Manage: COM Add-ins > Go, untick recent ones, and restart normally.
  3. Make sure Teams or Skype isn't grabbing Outlook first. Sometimes the Teams or Skype add-in tries to open Outlook before it's ready. Disable it via the COM Add-ins screen above and reopen Outlook.
  4. Repair the data file with scanpst.exe. If Outlook still won't start, your .pst/.ost data file may be damaged. Close Outlook and run SCANPST.EXE from your Office install folder — on modern Microsoft 365 it's usually C:\Program Files\Microsoft Office\root\Office16 (if you can't see it there, just search Windows for scanpst.exe). Point it at your data file, let it scan and repair. It offers to back up first — say yes.
  5. Last resort — a fresh mail profile. Go to Control Panel > Mail (Microsoft Outlook) > Show Profiles > Add, create a new profile and set Outlook to use it. For a mailbox on the server (Microsoft 365/Exchange/Outlook.com) your mail re-downloads automatically. For a POP account, back up your existing .pst first so nothing is lost.

Never delete your .pst or .ost file to "start clean" without a backup — for a POP account that is your only copy of your mail. If you're unsure which type you have, stop here and let us check before anything is removed.

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Need a hand with the wider mailbox? We also help with Microsoft 365 support, day-to-day email support and fast remote IT support across IT support in Dorset. Prefer to just talk it through? Get in touch.

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// GOOD QUESTIONS

Frequently asked

What does "the set of folders cannot be opened" mean in Outlook?

It's part of the same classic-Outlook startup error and usually points to a corrupt navigation-pane file or a damaged data file. Running outlook.exe /resetnavpane rebuilds the layout file and fixes it most of the time; if not, repair the data file with scanpst.exe.

Will outlook.exe /resetnavpane delete my emails?

No. It only resets the navigation pane — the folder list, favourites and shortcuts down the left. Your emails, calendar and contacts are untouched. You may just need to re-pin a favourite folder afterwards.

I typed outlook.exe /resetnavpane and nothing happened — what now?

Check the spacing (there's a space before the slash) and that Outlook is fully closed first. If it runs but the error returns, move on to Safe Mode (outlook.exe /safe) to rule out an add-in, then scanpst.exe to repair the data file.

Does this apply to the New Outlook as well?

No — this error and the /resetnavpane command are for classic Outlook for Windows. The New Outlook is a rebuilt app that doesn't use the same navigation-pane file. If you're on New Outlook, the fix is different, so give us a call and we'll sort the right one.

Could an add-in like Teams or Skype be stopping Outlook opening?

Yes. The Teams or Skype add-in occasionally tries to launch Outlook before it's ready and blocks it. Start Outlook with outlook.exe /safe, and if it opens, disable that add-in under File > Options > Add-ins > COM Add-ins.

Can 365 Techies fix this remotely?

Yes, and it's usually a five-minute job. We connect through Splashtop SOS — you watch the whole time, we phone you first, and access ends the moment it's done. Call 01202 775566. Home support is £18.25/month per computer if you'd like us to keep an eye on things afterwards.

// Still stuck?

Still staring at the error?

If /resetnavpane, safe mode and a repair haven't done it, don't keep poking at settings and risk your mailbox. Call 365 Techies on 01202 775566 — we watch over your shoulder on Splashtop (you see everything, we phone you first, access ends the moment it's fixed) and usually have classic Outlook opening again within minutes.

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