Fix Outlook Not Responding When Sending or Replying

If Outlook freezes or shows “Not Responding” when you send or reply to an email, the fix usually involves disabling add-ins, repairing the data file, or updating Office. This article walks through the most effective solutions in order, from quick checks to deeper repairs.

Why Outlook Freezes on Send or Reply

Outlook is a complex application that depends on your email account settings, local data files, and installed add-ins. When you click Send or Reply, Outlook must compose a new message window, check for errors, and connect to your mail server. A freeze at this moment often points to one of these culprits:

• Add-ins – Third-party extensions (like CRM tools, grammar checkers, or PDF converters) can conflict with Outlook’s compose window.
• Corrupted data file – Your local .pst or .ost file may be damaged, causing delays when reading or writing messages.
• Outdated Office version – Bugs in older builds are frequently fixed in updates.
• Large or complex emails – Replying to a thread with hundreds of images or a huge attachment can strain the client.
• Profile or account issues – A misconfigured mail profile or a server timeout can cause Outlook to hang while trying to send.

Identifying the exact cause is the first step, but trying the fixes below in order usually resolves the issue without needing to know the root cause.

Start With These Quick Checks

Before diving into deeper repairs, try these simple steps—they often solve the problem in seconds.

1. Restart Outlook – Close the app completely (check the system tray for the Outlook icon, right-click it, and choose Exit). Then reopen it.
2. Restart your computer – This clears temporary glitches and frees up memory that Outlook may need.
3. Check your internet connection – Outlook needs to reach your mail server. If you’re offline, sending will hang. Look for the “Working Offline” button in the Send/Receive tab and make sure it’s not highlighted.
4. Update Office – Go to File > Office Account > Update Options > Update Now (or Help > Check for Updates on Mac). Install any pending updates and restart Outlook.

If Outlook still freezes, move on to the more targeted solutions below.

Disable Problematic Add-Ins

Add-ins are the most common cause of Outlook freezing, especially when composing or replying. They run inside Outlook and can interfere with the message window. To disable them:

1. In Outlook, go to File > Options > Add-ins.
2. At the bottom, next to “Manage,” select COM Add-ins from the dropdown and click Go….
3. Uncheck all the add-ins in the list, then click OK.
4. Restart Outlook and try sending a test email.

If that fixes the issue, re-enable add-ins one at a time to find the culprit. Common offenders include:

• Skype for Business or Teams Meeting add-ins
• Adobe Acrobat PDFMaker
• Grammar or writing assistant tools
• CRM or productivity extensions

If you don’t want to disable an add-in permanently, try updating it to the latest version—it may have a compatibility fix.

Repair Your Outlook Data File

If add-ins aren’t the problem, your local data file might be corrupted. Outlook stores your emails in a .pst (for POP accounts) or .ost (for IMAP/Exchange). You can repair it with the built-in tool:

1. Close Outlook.
2. Open the Run dialog (Windows key + R) and type: scanpst.exe (for .pst files) or scanost.exe (for .ost files). If you don’t know which one, try scanpst first.
3. In the tool, click Browse to find your data file. The default location is:
   C:\Users\[YourUsername]\AppData\Local\Microsoft\Outlook
4. Select the file and click Start. The tool will check for errors and offer to repair them.
5. After it finishes, reopen Outlook and test sending a message.

If scanpst can’t fix the file, you may need to create a new Outlook profile (see next section).

Create a New Outlook Profile

A corrupted mail profile—which stores your account settings, server names, and passwords—can also cause freezes. Recreating it is safe and doesn’t delete your emails (they stay on the server or in the data file).

1. Open the Control Panel and search for Mail (or Mail (32-bit)).
2. Click Show Profiles.
3. Click Add and give the new profile a name (e.g., “OutlookNew”).
4. Follow the prompts to add your email account. You may need your email password.
5. Once created, select Always use this profile and choose the new profile from the dropdown.
6. Restart Outlook. It will set up the new profile and download your mail again.

This often resolves freezes that persist after other fixes. You can delete the old profile later once you confirm everything works.

Run Outlook in Safe Mode

Safe Mode starts Outlook without add-ins and with basic settings. It helps determine if the problem is related to add-ins or something else.

1. Press Windows key + R, type outlook /safe, and press Enter.
2. If Outlook opens and sending works fine, then an add-in is the culprit. Go back to the Add-ins section and disable them.
3. If it still freezes, the issue is likely with your data file or profile, so try the repair or profile steps above.

Note: In Safe Mode, some features like custom navigation panes may be disabled, but that’s normal.

Check for Large Attachments and Email Size

Sometimes the freeze happens because you’re trying to send a very large attachment or replying to a massive email thread. Outlook has a default size limit (often 20-25 MB), but even smaller attachments can cause issues if your internet connection is slow or the mail server is having problems.

• Try removing the attachment and sending the email without it.
• If you’re replying to a long thread, start a new email instead of hitting Reply.
• Empty your Deleted Items and Sent Items folders to reduce the size of your data file.

If you frequently send large files, consider using a cloud storage link (like OneDrive or Google Drive) instead of attaching the file directly.

Frequently Asked Questions

Why does Outlook freeze only when I reply to certain emails?

This usually happens when the original email contains many inline images, unusual formatting, or a large number of recipients. The reply window tries to load all that content, which can overwhelm Outlook. Try replying in plain text format (change it in the Format Text tab) or forwarding the email instead of replying. If the issue is specific to one email, it may be corrupted—ask the sender to resend it.

Will I lose my emails if I create a new profile?

No. Your emails are stored in the .pst/.ost file or on the server. Creating a new profile just changes the settings Outlook uses to connect to your account. Once you set up the new profile, you’ll see your emails again (they may take a few minutes to download). If you have a POP account, make sure you know your email password and server settings, as you’ll need to enter them again.

How do I update Outlook if the update button is grayed out?

If the Update Now button is unavailable, it may be because your Office installation is managed by an organization (work or school). In that case, contact your IT administrator. For personal Office, try closing Outlook and running Windows Update, which often includes Office updates. You can also go to Control Panel > Programs > Microsoft Office and choose “Change” then “Quick Repair” to fix installation issues.

What is the difference between a .pst and .ost file?

A .pst (Personal Storage Table) is used for POP and IMAP accounts—it stores copies of your emails locally. An .ost (Offline Storage Table) is used for Exchange and Microsoft 365 accounts; it’s a cached copy that syncs with the server. When repairing, use scanpst for .pst and scanost for .ost. If you’re unsure, check the file location mentioned earlier—both types are usually in the same folder.

Can a slow internet connection cause Outlook to freeze?

Yes. When you send an email, Outlook must connect to your mail server. If the connection is slow or unstable, Outlook may appear frozen while waiting for a response. Check your internet speed, and if you’re on Wi-Fi, try moving closer to the router or using an Ethernet cable. Also, disable any VPN or proxy that might interfere with Outlook’s connection.

What should I do if none of these fixes work?

If Outlook still freezes after trying all the steps, consider repairing your Office installation. Go to Control Panel > Programs > Microsoft Office > Change and select Quick Repair first. If that doesn’t help, try Online Repair (which takes longer but is more thorough). As a last resort, you can back up your data and reinstall Office completely.

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