Microsoft Outlook not opening or sending emails stops work cold. It's one of the most reported problems across both home users and small businesses, and it shows up in a few distinct ways: Outlook refuses to launch, it opens but hangs on the loading screen, or it opens fine but emails sit in the Outbox and never actually send. The fix depends on which of those you're seeing, so this guide works through each scenario in order.
Start here: quick checks before anything else
Before changing any settings, run through these three checks. They resolve a surprising number of Outlook failures in under two minutes.
- Restart Outlook as administrator. Right-click the Outlook icon and choose "Run as administrator". A permissions conflict with Windows can prevent Outlook from loading correctly.
- Check your internet connection. Outlook needs a live connection to reach Microsoft Exchange or Microsoft 365. If your Wi-Fi or NBN connection is the issue, Outlook will appear broken when it isn't.
- Look for Windows or Office updates. Open Windows Update and let any pending updates install. A partially applied Office update can corrupt Outlook's startup state.
If none of those solve it, work through the sections below that match your specific problem.
Fix Outlook when it won't open at all
When Outlook refuses to launch or freezes on the "Loading Profile" screen, the cause is almost always one of three things: a corrupt Outlook profile, a faulty add-in, or a damaged data file.
Try safe mode first
Hold the Windows key, press R, type outlook.exe /safe, and press Enter. Safe mode disables all add-ins. If Outlook opens in safe mode, an add-in is the culprit. Go to File, Options, Add-ins, then set the Manage dropdown to "COM Add-ins" and click Go. Disable every add-in, restart Outlook normally, then re-enable them one at a time to find which one is broken.
Create a new Outlook profile
Open Control Panel, search for "Mail", and click Mail (Microsoft Outlook). Select "Show Profiles", then "Add" to create a new profile. Walk through the account setup wizard with your email address. Set the new profile as the default and restart Outlook. A corrupt profile is the single most common reason Outlook won't load on Windows 10 and Windows 11.
Repair the Outlook data file
Outlook stores your emails, contacts, and calendar in a .pst or .ost file. When that file is damaged, Outlook can't finish loading. Microsoft includes a repair tool called ScanPST.exe (also called the Inbox Repair Tool) with every Office installation. Find it by searching your C: drive for "SCANPST.EXE", open it, browse to your data file (typically in C:\Users\YourName\AppData\Local\Microsoft\Outlook), and run the scan. The tool fixes most corruption without data loss.
Run an Office repair
If safe mode, a new profile, and ScanPST all fail, repair the Office installation itself. Go to Settings, Apps, find Microsoft 365 (or Microsoft Office) in the list, click Modify, and choose "Online Repair". This replaces damaged Office files from Microsoft's servers. It takes roughly 15 minutes and doesn't remove your data.
Fix Outlook when emails are stuck in the Outbox
Emails stuck in the Outbox are a separate problem from Outlook not opening, though both can happen at once. The most common causes are a large attachment that exceeded the server's size limit, an authentication error with your mail server, or Outlook being set to work offline.
Check the Work Offline setting
This is the most overlooked fix. Open Outlook and click the Send/Receive tab at the top. If "Work Offline" is highlighted or bold, click it once to toggle back online. Outlook can switch to offline mode automatically when it loses a connection, and it won't warn you clearly when it does.
Delete the stuck email and resend
Open the Outbox folder. Right-click the stuck email and choose Delete. If Outlook won't let you delete it because it's "being sent", go to Send/Receive, click "Work Offline" to pause sending, then delete the message, and toggle back online. Recompose the email and check the attachment size. Most Microsoft 365 accounts block attachments over 25 MB by default.
Re-enter your account password
An expired or changed password causes Outlook to silently queue outgoing mail without explaining why. Go to File, Account Settings, Account Settings again, select your email account, and click Change. Re-enter your current password. If your organisation uses Microsoft Entra (formerly Azure AD) for authentication, you may need to sign out of Office entirely and sign back in through File, Office Account.
Check your SMTP settings
If you're using a non-Microsoft email account (such as a business email hosted elsewhere), the SMTP server details may have changed. Go to File, Account Settings, Account Settings, select your account, and click Change. Under "More Settings", open the Outgoing Server tab and confirm the SMTP address, port, and encryption match what your email provider currently requires. Port 587 with STARTTLS is the standard for most providers now. Port 465 with SSL is also common.
Fix Outlook when it keeps crashing after opening
Outlook opening then crashing a few seconds later usually points to a software conflict or a corrupted navigation pane configuration.
Reset the navigation pane by closing Outlook, pressing Windows + R, typing outlook.exe /resetnavpane, and pressing Enter. This clears the navigation pane configuration file without touching your emails. It's a fast fix that resolves crashes caused by a corrupt pane layout.
If crashing continues, check whether a recent Windows update or antivirus update changed something. Some antivirus tools scan Outlook's data files in real time, which can cause Outlook to crash when the scan conflicts with Outlook's own file access. Temporarily disabling real-time scanning (for a test only) will confirm if this is the cause. If it is, add your Outlook data file folder to your antivirus exclusion list rather than leaving protection disabled.
When to get help
Most Outlook problems respond to the fixes above. If you've worked through all of them and Outlook still won't open or send, the problem is likely specific to your system configuration, your organisation's server settings, or a corrupt Windows user profile. These cases are genuinely hard to self-diagnose from a list.
If your business relies on Outlook and downtime is costing you, remote IT support can resolve most Outlook failures without anyone needing to visit your office. A technician can connect to your machine, inspect the Outlook logs, test the mail server connection, and apply fixes directly. It's faster than working through forum threads and doesn't require shipping your computer anywhere. If you're weighing up the cost, it helps to understand what remote IT support actually costs in Australia before committing.
Outlook failures tend to come in clusters. Fixing the immediate problem is worth doing, but it's also worth checking whether Windows is fully updated, whether your Office licence is current, and whether your email account passwords are set to never expire unexpectedly. Those three things prevent most repeat failures before they start.