Windows · critical · Microsoft Office

"Cannot start Microsoft Outlook. Cannot open the Outlook window"

Outlook fails at launch with a dialog and never draws a window. In most cases the mailbox is fine and the damage is to the small local files that describe the layout — which are disposable.

What you see

A dialog appears within a second or two of launching: "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened." Sometimes the message names an invalid XML file instead. Outlook on the web works normally for the same account.

What is actually wrong

Outlook keeps the navigation pane layout in a small XML file beside the profile. A crash or a full disk can leave it half written, and Outlook will not start rather than ignore it. Behind that, the same message is produced by a damaged profile, an OST that cannot be opened, or an add-in that fails during startup.

Codes and articles

Cannot start Microsoft OutlookCannot open the Outlook windowThe set of folders cannot be openedresetnavpaneoutlook safe mode

Start here — find out which fix applies

A script that runs the 3 inspection commands from the write-up below and prints what each one returned. It reads the machine and changes nothing — every command that could write, delete, start or stop is excluded from it by construction. Run this first, then pick the fix its output points at.

Download the read-only diagnosticchanges nothing · safe to run before reading

Fixes (3)

Reset the navigation pane

Run dialog, as the affected user10 minuteslow riskreversible

Always try this first. It takes a minute and it is the cause most of the time.

Close Outlook completely, including any process left running.
PowerShell
```
Get-Process OUTLOOK -ErrorAction SilentlyContinue | Stop-Process -Force
```
Look at the navigation pane file before deleting it, so you know whether it is the problem.
PowerShell
```
Get-ChildItem "$env:APPDATA\Microsoft\Outlook" -Filter '*.xml' | Select-Object Name, Length, LastWriteTime
```
A zero-length or truncated profilename.xml is the signature of this fault. If the file is a sensible size and dated before the problem started, the navigation pane is probably not the cause and you should move on rather than deleting it.
Start Outlook with the reset switch.
Command Prompt
```
outlook.exe /resetnavpane
```
If that does not help, reset the views as well — a damaged view definition produces the same dialog.
Command Prompt
```
outlook.exe /cleanviews
```

Confirm it workedOutlook opens to the inbox and the folder list is present.

If you need to undo itNeither switch can be undone, but neither touches mail. What is lost is cosmetic: /resetnavpane clears Favourites and any shortcuts in the navigation pane, and /cleanviews returns custom folder views to their defaults. Warn the user about Favourites before you run it — for someone who works from a curated favourites list, rebuilding it is the only real cost of this fix.

Download this fix as a PowerShell scriptasks before each step

Find the add-in that is failing at startup

PowerShell as the affected user40 minuteslow riskreversible

Outlook starts in safe mode but not normally. Safe mode loads no add-ins, so this narrows it to one of them.

Start Outlook in safe mode to get a working window.
Command Prompt
```
outlook.exe /safe
```
List what is registered to load, so you know what you are bisecting.
PowerShell
```
Get-ChildItem 'HKCU:\Software\Microsoft\Office\Outlook\Addins','HKLM:\SOFTWARE\Microsoft\Office\Outlook\Addins' -ErrorAction SilentlyContinue | ForEach-Object { [pscustomobject]@{ Addin = $_.PSChildName; LoadBehavior = (Get-ItemProperty $_.PSPath).LoadBehavior } }
```
LoadBehavior 3 means load at startup, 2 means loaded once and disabled after a failure, and 0 means off. An add-in sitting at 2 has already crashed Outlook at least once and is a strong suspect.
In safe mode, go to File → Options → Add-ins → Go, and clear every COM add-in. Restart normally to confirm Outlook now opens.
Re-enable them one at a time, restarting between each, until the failure returns. The last one enabled is the culprit.
Leave the culprit disabled and take it up with whoever supplies it. Update it before assuming it must stay off — this is usually fixed in a later build.

Confirm it workedOutlook starts normally with every add-in enabled except the one identified.

If you need to undo itRe-tick any add-in you disabled. Nothing is removed by this process.

Download this fix as a PowerShell script3 steps you do yourself · asks before each step

Build a new mail profile

Control Panel → Mail, as the affected user45 minutesmedium riskreversible

The pane reset did not help and safe mode fails too, or the mailbox has been moved between servers or tenants.

Record the account details and the path of any PST files in use before you start.
PowerShell
```
Get-ChildItem 'HKCU:\Software\Microsoft\Office\16.0\Outlook\Profiles' | Select-Object PSChildName
```
Local PST archives are not carried into a new profile, and their absence afterwards is the thing most often reported as data loss. Note the paths now and re-attaching them later is two clicks.
Open the Mail control panel and create a new profile rather than repairing the existing one.
Command Prompt
```
control mlcfg32.cpl
```
Set Outlook to prompt for a profile, so you can switch back to the old one if the new one is worse.
Add the account and let autodiscover configure it. Do not enter server settings by hand for a Microsoft 365 mailbox.
Re-attach any PST files via File → Open & Export → Open Outlook Data File.
Once the new profile is proven over a day or so, set it as default and remove the old one.

Confirm it workedOutlook opens on the new profile, mail sends and receives, and every archive that was attached before is present.

If you need to undo itThe old profile is untouched until you delete it — pick it at the profile prompt to go back.

Download this fix as a PowerShell script4 steps you do yourself · asks before each step

Related faults

Where this stops. This write-up was written and checked by hand. It says what each step changes, how to confirm it worked and how to reverse it, and anything destructive is flagged before you reach it. If it does not match what your machine is doing, search the Support Centre for the exact code or message — and when something needs a person, get in touch.