Troubleshooting Guide: Resolving Issues with Outlook Not Sending Emails

Sometimes, you encounter a situation when your Outlook fails to send emails. All the messages are stuck in the Outbox folder. Such an issue can hinder your workflow and productivity in a significant manner. Therefore, it is important to resolve this ‘Outlook not sending emails issue as soon as possible. In this post, we will discuss the solutions to quickly resolve the Outlook not sending emails issues. But before moving on, let’s understand the reasons why this issue occurs. 

Why Outlook is Not Sending Emails?

Here are some common reasons for Outlook not sending emails issue.

  • Unstable Internet Connection – Outlook requires a stable internet connection to synchronize with the mailbox server and send and receive emails. Any kind of network connectivity issues may prevent Outlook from sending new emails.
  • Corrupt Outlook Data File – If the Outlook data (PST) file is corrupt or damaged, it can lead to issues in sending emails.
  • Damaged Outlook Installation – When the installation files of Outlook get damaged or corrupted, it can prevent Outlook from sending emails.
  • Incorrect Email Account Settings – When the email account settings are incorrect, you may face issues when sending emails in Outlook. 
  • Outdated Outlook Application Version – Outdated version of Outlook can lead to incompatibility issues and may prevent sending emails.
  • Faulty Add-ins – Faulty or incompatible add-ins can lead to issues in Outlook and prevent it from sending emails.

Solutions to Troubleshoot and Fix the Outlook not Sending Emails Issue

Here are some solutions you can try to fix the email-sending issue in Outlook.

Method 1: Check the Internet Connection

The first step is to check the network connection. You can try to access different websites to confirm if the connection is working and stable. If it is not working, restart the router or contact your internet service provider.

Method 2: Check the Outbox Folder

Sometimes, emails with large attachments get stuck in the Outbox folder. So, check the Outbox folder for emails with large attachments. Here’s how:

  • Open Outlook and click on the Outbox folder.
  • Check for all unsent emails that have large attachments.
  • If you find any such emails, remove the attachments or upload them to a cloud storage and then send the storage links with the email.

Method 3: Check and Reduce Mailbox Size

If your mailbox size exceeds the storage quota, then you may face issues while sending emails. You can check and reduce the mailbox size to resolve the issue. Follow these steps:  

  • Open Outlook and go to File > Info > Tools.
  • Select Mailbox Cleanup.
  • Click View Deleted Mailbox Size to check the mailbox size.
  • If the mailbox quota is exceeding the limit, click Close. 
  • Then, use the Mailbox Cleanup window to clear the deleted folders and remove unnecessary mail items.

Method 4: Repair Outlook Installation

To repair the damaged Outlook installation files, follow the below steps:

  • Go to Control Panel.
  • Click Programs and Features and select Microsoft Office.
  • Click Change.
  • Choose Online Repair, Repair, or Quick Repair based on the installed Microsoft Office version. 
  • Follow the on-screen instructions to complete the repair process.
  • Restart Outlook and check if the issue has been resolved.

Method 5: Update Outlook Application

If your Outlook is not updated, you may face issues with your Outlook application. You can check and install the latest Outlook updates. Follow the below steps:

  • Open Outlook.
  • Go to File > Office Account.
  • Under Product Information, click on Update Options > Update Now.
  • Follow the on-screen instructions to complete the update process.
  • Once the update process is completed, restart Outlook.

Method 6: Create a New Outlook Profile

If your Outlook profile is corrupted, you may encounter the Outlook not sending emails issue. To resolve this, you can create a new Outlook profile. Follow the below steps:

  • Go to Control Panel.
  • Click Show Profiles > Add.
  • Enter a new profile name and click OK.
  • Configure the email account settings.
  • Set the new profile as default by choosing the new profile in the ‘Always use this profile’ option in the dropdown menu. Click OK.
  • Check if the email-sending issue has been resolved.

Method 7: Enable TCP/IP Protocol

If the TCP/IP is not set as your default protocol, then Outlook may fail to send the emails. You can enable the TCP/IP protocol by following the below steps:

  • Go to Windows Search Bar.
  • Type the ncpa.cpl and press Enter.
  • Go to Network Connections, right-click on the Internet Connection, and select Properties.
  • In the Networking tab, check if the Internet Protocol Version 6 (TCP/IPv6) is checked or not. If it is not, check it and click OK.

Method 8: Turn on Authentication 

Follow the below steps to turn on authentication in Outlook:

  • Open Outlook.
  • Go to File > Account Settings.
  • Click on Manage Profiles.
  • In the Mail Setup window,click on Email Accounts.
  • Select your account and click Change.
  • In the Change Account window, click on More Settings.
  • In the Outgoing Server tab, check the box ‘My outgoing server (SMTP) requires authentication.’
  • Select the option ‘Use the same setting as my incoming mail server’ and click OK.
  • Click Next and click Finish.

Method 9: Disable Faulty Add-ins

Faulty or incompatible add-ins can also cause issues while sending emails. Disabling the add-ins can help in fixing the Outlook not sending emails issue. Follow the below steps:

  • Press Windows+R to open the Run prompt.
  • Enter outlook.exe /safe and click OK to open Outlook in safe mode.
  • Click on File and select Options.
  • Click on Add-ins, select COM Add-ins in the Manage box, and click Go.
  • Uncheck the plugins to disable them.

Method 10: Repair the PST File

If the above methods do not resolve the issue, this means that the Outlook data (PST) file is damaged or corrupted. You can use the default Inbox Repair Tool (ScanPST.exe) provided by Microsoft to repair corrupted PST file. Follow the below steps:

  • Close Microsoft Outlook.
  • Locate the ScanPST.exe file. Follow the below path to find it:
  • C:\Program Files\Microsoft Office\root\Office16
  • Run ScanPST.exe.
  • Click Browse and select the PST file that needs to be repaired.
  • Click Start.
  • If there are any errors in the PST file, click on Repair.
  • Click Close when the repair process is completed.

If the above tool fails to repair the corrupt PST file, then you can use an advanced PST repair tool, such as Stellar Repair for Outlook. The tool can repair the corrupt PST file and recover all the data by keeping the hierarchy and folder structure intact. It allows you to save the repaired data in new Outlook PST that you can easily import into your Outlook account.


There are various reasons why Outlook fails to send new emails, such as poor or no internet connectivity, incompatible add-ins, damaged or corrupted Outlook data files, etc. By following the solutions mentioned above, you can resolve the Outlook not sending emails issue. If the issue occurs due to a corrupt PST file, you can use Stellar Repair for Outlook to quickly repair the PST file. 

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