How to Fix Outlook not Sending Emails on Windows 10/11?

Outlook is one of the most popular email and calendaring applications used by businesses and professionals across the globe. However, sometimes, temporary issues with the email client, the Offline Outlook data file (OST), or the Windows system can lead to issues that can prevent Outlook users from sending or receiving new emails.

In this article, you will learn the reasons that can lead to the “Outlook not sending emails on Windows 10/11” issue. You will also learn the workarounds and solutions to effectively troubleshoot and resolve this issue. In case the OST file is in an accessible state, then use the 3rd party OST to PST converter tool to export the data from the OST file for further use.

Reasons for Outlook is not Sending Emails

Outlook users may face difficulties in sending emails in Outlook on Windows 10/11 due to several factors, such as:
  • Unstable or unreliable internet connection
  • Wrong recipient address
  • Inconsistent or oversized Outlook OST file
  • Wrong or outdated Outlook password
  • Incorrect server settings or misconfigured email account settings
  • Large or multiple attachments
  • Software conflicts
  • Wrong antivirus or firewall settings
  • Outdated Outlook
  • Temporary server-related issues

Solutions to Troubleshoot and Resolve Outlook not Sending Emails on Windows 10/11

Follow the below solutions in the given order to effectively troubleshoot and resolve the Outlook not sending emails on Windows 10/11 issue.

Before moving to the solutions, do the following:
  • Often, you make mistakes when typing the email addresses. Therefore, you must check that the email you are sending has the correct address in the To, Cc, and Bcc fields. There should be no special characters or wrong spelling as that can lead to failure in sending email.
  • Check Work Offline is not enabled. If enabled, you can disable it to allow Outlook to send emails. You can find this option under the Send/Receive tab.
  • Make sure the email you are sending does not have large attachments or too many attachments.
  • If your password has been changed recently or expired, then check if you’re entering the new password.
After verifying the above, try to resend the email.

1. Check and Fix Network Connection Issues

Double-check if your internet is working and there are no firewall conflicts with Outlook. To check whether the internet is working and the server is online,
  • Restart the router and modem and check the Ethernet cable for proper connection.
  • Open a web browser and then launch any website. If it loads, the internet is working fine.
  • Go to the Outlook web app in the web browser and try to sign in. If you can’t log in, you can wait and try again after some time. It’s possible that the server is under maintenance and may come online after a while.
Also, check the firewall rules and make sure it is not blocking any ports used by Outlook and your email service provider.

2. Update Outlook and Windows

Updating Outlook and Windows can help resolve compatibility issues that can be a reason preventing Outlook from sending emails. To update Outlook, follow these steps:
  • Open Outlook and go to File > Office Account > Update Options.
  • You will see an option ‘Update Now.’ Click on it and then let Outlook check for new updates.
  • If Outlook finds the new updates, it will show you. You can then follow the update wizard to install and apply the updates.
To update Windows 10/11, follow these steps:
  • Press the Windows key on the keyboard and then click on Settings (gear icon).
  • Click Update & Security and then click Windows Update.
  • Click the Check for updates button. If any updates are available, download and install them.
Once updated, restart the system and then check if you can now send emails in Outlook.

3. Use the Microsoft SaRA Tool

If you are using a Microsoft 365 or Office 365 email account, you can use the Microsoft Support and Recovery Assistant (SaRA) tool to troubleshoot and resolve issues preventing Outlook from sending new emails. The steps are as follows:
  • Download and run the SaRA tool on your Windows 10/11 PC. The installation is straightforward just like installing any other software. However, you will need administrator permissions to install and run the SaRA tool.
  • After the installation, launch it and then follow the onscreen instructions.
  • Based on your selections, SaRA will scan the system and detect issues preventing Outlook from sending new emails.
  • The SaRA tool will try to resolve the issues. Otherwise, it can provide solutions that you can apply to resolve the issues.

4. Disable or Remove Incompatible or Faulty Add-Ins

Incompatible or faulty add-ins can also result in the Outlook not sending emails issue. Follow the below steps to find and remove the faulty add-ins.
  • Close Outlook.
  • Hold the SHIFT key and double-click on the Outlook icon to launch it in Safe mode.
  • Then, click File > Options > Add-ins.
  • Find and click on the Go button.
  • Unselect all add-ins and click OK to disable them.
  • Then close Outlook and start it again normally - not in safe mode.
  • Try sending a new email. If the email is sent successfully, activate one add-in at a time and restart Outlook.
  • Send a test message and check if Outlook can send and deliver the message.
  • If the message delivery fails after activating one of the add-ins, select it and click Remove. This will uninstall and remove it from Outlook and fix the Outlook not sending emails issue permanently.

5. Create a New Profile

Creating a new profile will replace your corrupt or damaged Outlook profile which could be a reason why Outlook is not sending emails on your Windows 10 or Windows 11 system. Follow the below steps to create a new profile and resolve the problem:
  • Open the Control Panel.
  • Click User Accounts and then click on Mail.
  • Click Show Profiles and then click the Add button.
  • You can type or enter any name for this new profile based on your convenience. Once entered, click OK.

  • You will see a new account sign-in wizard. Enter the email account username and password to sign into this new profile.
  • Once signed in successfully, click Next and then Finish.
  • You can then choose ‘Always use this profile’ and then select your new profile name from the dropdown. This will set your new profile as default. 
  • Alternatively, you can delete the old profile. However, doing that will also remove your old OST file. So, backup the OST file before applying these advanced solutions.
  • Once done, click Apply > OK and then restart the Outlook.

6. Rebuild Outlook Data File (OST)

Inconsistent, oversized, or large OST files can cause a plethora of issues in Outlook as it fails to store new messages or synchronize changes with the mailbox server. If Outlook fails to sync with the server, it cannot send emails. In such a case, you can create a new OST file and resolve the inconsistency issue with the existing OST file. The steps to rebuild the OST file are as follows:
  • Close Outlook and press the Windows + R keys.
  • In the Run window, type %localappdata%/Microsoft/Outlook and click OK. You can also press the Enter key to open the default OST file location.
  • Copy or rename the OST file with the .bak extension to create a backup copy. This OST backup can help in restoring missing emails after resolving the issue.
  • After the backup, you can delete the original OST file and start Outlook.
  • Outlook won’t find the old OST file and hence, creates a new OST file. It will sync (download) all mail items from the mailbox server.
  • After the sync is complete, send a new email. It should be sent immediately.
Once the error is resolved, check all your mail folders and mail items. If there are missing emails or mail items, use an OST to PST converter software such as Stellar Converter for OST to extract the missing mail items from the backup OST file to a new Outlook importable PST file. Then, you can import this PST file into your Outlook’s new profile or new OST file and restore all mail items. The software also comes in handy when you need to extract and restore mail items from inaccessible, oversized, or orphaned Outlook OST data files.


Troubleshooting the Outlook not sending emails issue on Windows 10/11 requires a systematic approach. This includes identifying and addressing the underlying causes that might be preventing Outlook from sending emails. This article discussed the solutions to troubleshoot and resolve the Outlook not sending emails on Windows 10/11 issue.
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