Apps · Repair guide

How to fix Outlook not responding

Error messageMicrosoft Outlook (Not Responding)

10 fixes, easiest first5 min readUpdated November 2026

Quick fix

Wait a few minutes, check for a hidden pop-up with Alt+Tab, then end Outlook in Task Manager and restart the PC. If classic Outlook keeps freezing, start it with outlook /safe and turn off add-ins; if that doesn't help, run Quick Repair on Microsoft 365.

What it means

"Not Responding" means Outlook has stopped reacting to clicks, usually because it is busy, waiting on a hidden prompt, or stuck on a faulty add-in, damaged data file or broken install. There are two Windows versions, classic Outlook and new Outlook for Windows, and some fixes only apply to one of them. Your email is normally stored safely on the mail server, so most fixes don't touch your messages.

Common causes

  • Outlook is busy with a large task, such as syncing lots of mail
  • A dialog box is waiting for an answer behind another window
  • A faulty or outdated add-in (classic Outlook)
  • Missing Office or Windows updates
  • Damaged Office program files
  • A damaged Outlook data file or profile (classic Outlook)

How to fix it

Work down the list. Each fix is safe to try before moving on to the next.

01Check which Outlook you haveEasy

  1. Look at the top-right corner of the Outlook window.
  2. If you see a toggle called Try the new Outlook, you are using classic Outlook.
  3. If you see a toggle called New Outlook, or the Help tab offers Go to classic Outlook, you are using new Outlook for Windows.
  4. Some work or school accounts hide the toggle. New Outlook looks much like Outlook on the web, while classic Outlook has the older ribbon with a File tab.
  5. Note your version; several fixes below say which one they are for.

Why it helps: Classic and new Outlook are different apps, so the right fix depends on which one you use.

02Wait, check for hidden pop-ups, then restart OutlookEasy

  1. Look at the status bar at the bottom of Outlook. If it is syncing or processing many messages, give it a few minutes.
  2. Press Alt + Tab to look for a dialog box waiting for an answer, and answer it.
  3. If Outlook is still frozen, right-click Start, select Task Manager, select Microsoft Outlook and choose End task.
  4. Make sure Outlook no longer appears in Task Manager, then open Outlook again.
  5. If that doesn't help, restart the PC.
  6. On a Mac: press Option + Command + Esc, select Outlook and choose Force Quit.

Why it helps: A long task or an unanswered prompt is the most common reason Outlook looks frozen.

03Check your mail in Outlook on the webEasy

  1. Make sure the PC is online by opening any website.
  2. In a browser, sign in to Outlook on the web (Outlook.com for personal accounts, or your organization's Outlook on the web for work accounts).
  3. If the web version works, your account is fine and the problem is in the Outlook app on this PC; carry on with the fixes below.
  4. If the web version also fails or is very slow, the problem may be with the mail service or your account. Wait a while or contact your email provider or IT team.

Why it helps: This tells you whether to fix the app on your PC or wait for a service problem to clear.

04Install Office and Windows updatesEasy

  1. Open Settings > Windows Update, select Check for updates, install everything and restart.
  2. Classic Outlook: open Outlook (or Word if Outlook won't open), go to File > Office Account (in Word: File > Account), then select Update Options > Update Now.
  3. If you don't see Update Now, select Enable Updates first.
  4. New Outlook: it updates itself automatically, so there is nothing to install by hand. Closing and reopening it lets a waiting update finish.
  5. On a Mac: in Outlook choose Help > Check for Updates, then select Update.

Why it helps: Microsoft regularly fixes freezes and crashes in updates.

05If you use classic Outlook, start it in safe mode and turn off add-insMedium

  1. Close Outlook.
  2. Press Windows + R, type outlook /safe and select OK. This only works for classic Outlook.
  3. If Outlook works in safe mode, an add-in is the likely cause. Go to File > Options > Add-ins.
  4. Next to Manage, choose COM Add-ins and select Go.
  5. Clear the check box for one add-in, select OK, then close Outlook and open it normally.
  6. Repeat one add-in at a time until Outlook stops freezing. Leave the problem add-in off and check its maker's site for an update.

Why it helps: Safe mode starts Outlook without add-ins, which are a common cause of crashes and hangs.

06If you use classic Outlook, repair Microsoft 365Medium

  1. Close all Office apps.
  2. Right-click Start and select Installed apps.
  3. Find Microsoft 365 or Microsoft Office in the list, select the three dots next to it and choose Modify.
  4. Choose Quick Repair and select Repair. This repairs the whole Office suite.
  5. If the problem continues, run it again and choose Online Repair, which is more thorough but takes longer.
  6. Restart the PC when the repair finishes.

Why it helps: Repair replaces damaged Office program files without touching your email or documents.

07If you use new Outlook, repair the appMedium

  1. Close new Outlook.
  2. Open Settings > Apps > Installed apps, type Outlook in the search box and find Outlook (new).
  3. Select the three dots next to it and choose Advanced options.
  4. Select Repair, wait for the check mark, then open Outlook again. Repair does not delete the app's data.

Why it helps: Repair fixes the app's files without removing your settings or accounts.

08If you use classic Outlook, repair your Outlook data fileAdvancedBack up first

  1. Warning: the repair tool changes your .pst file. It makes a backup first, but some damaged items may not be recoverable.
  2. Close Outlook.
  3. To find the file, open Outlook (if it starts) and go to File > Account Settings > Account Settings > Data Files, and note the location of the .pst file.
  4. This tool repairs .pst files only. Microsoft 365, Outlook.com and Exchange accounts normally use an .ost file instead, which this tool does not fix.
  5. In File Explorer, open the Office program folder, usually C:\Program Files\Microsoft Office\root\Office16 or C:\Program Files (x86)\Microsoft Office\root\Office16, and open SCANPST.EXE.
  6. Select Browse, choose your .pst file and select Start. If errors are found, select Repair.
  7. Run it again until no errors are found, then open Outlook. Recovered items may appear in a Lost and Found folder.

Why it helps: A damaged data file can make classic Outlook freeze or crash every time it opens.

09If you use classic Outlook, create a new profileAdvancedBack up first

  1. Warning: keep your old profile until the new one works. Deleting a profile removes the offline copy of mail stored on this PC; mail kept only on this PC (for example in a .pst file) can be lost, so back up any .pst files first.
  2. Close Outlook. Select Search, type Control Panel, open it, then go to User Accounts > Mail > Show Profiles.
  3. Select Add, type a name for the new profile and select OK.
  4. Enter your email address and password and finish the setup.
  5. Select Prompt for a profile to be used, then start Outlook and choose the new profile.
  6. Your mail downloads again from the server, which can take a while for a large mailbox.

Why it helps: A damaged profile can stop classic Outlook from starting; a fresh one rebuilds the settings.

10If you use new Outlook, reset or reinstall itAdvancedBack up first

  1. Warning: Reset and reinstall both delete new Outlook's data on this PC: its settings, saved sign-ins and the offline copy of your mail. You will need to sign in and may need to add your accounts again. Mail in online accounts such as Outlook.com, Microsoft 365 or Gmail stays on the server and downloads again.
  2. To reset: open Settings > Apps > Installed apps, find Outlook (new), select the three dots, choose Advanced options and select Reset, then confirm.
  3. Open Outlook, sign in and check whether it works.
  4. If it still fails, reinstall: open Start, find Outlook (new), right-click it and choose Uninstall.
  5. Open the Microsoft Store app, search for Outlook and select Get (or Open if it is already there).
  6. Sign in, and add your accounts again if they are not added automatically.

Why it helps: Reset gives the app a clean start, and a reinstall replaces a broken copy when repair doesn't help.

Check it's fixed

  • Outlook opens and stays responsive for a full day of normal use.
  • New mail arrives and you can send a test message to yourself.
  • Task Manager no longer shows Outlook as "Not responding".

When to get help

If Outlook still freezes after a repair and a new profile, or it fails on several PCs with the same account, contact your IT team or email provider. Work accounts may have add-ins or settings managed by your organization.

Questions

Why does Outlook say "Not Responding" and then come back?

Outlook is usually busy with a big task, such as syncing a large mailbox or opening a large attachment. If it happens often, check for add-ins and updates.

Will repairing Office delete my emails?

No. Repairing Office only replaces program files. Your email stays in your account and data files.

Can I use outlook /safe with new Outlook?

No. Safe mode with outlook /safe is for classic Outlook. For new Outlook, end it in Task Manager, then repair the app from Installed apps.

Can I switch back to classic Outlook if new Outlook won't load?

If classic Outlook is installed, you can open it from Start, or use Go to classic Outlook on the Help tab in new Outlook. Some work accounts control which version you can use.

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