Ms Outlook

Fix Outlook Outbox Not Sending Messages: Effective Solutions & Tips

When emails remain stuck in the Outlook outbox, it can be frustrating and impact productivity. This issue indicates that the email is unable to be sent for various reasons, essentially meaning that while the user has composed the message and clicked send, it remains in a state of limbo within the Outbox folder. Successful email delivery relies on various factors including internet connection, server settings, and file sizes. Understanding why this happens and how to effectively troubleshoot it is crucial.


Key Takeaways

  • Email stuck in Outbox: Indicates issues with sending messages.
  • Common culprits: Poor internet connection, large attachments, incorrect SMTP settings.
  • Effective troubleshooting: Involves verifying connection status, adjusting settings, and managing file sizes.
  • Best practices: Regularly clear cache, keep Outlook updated, and ensure proper settings.

Possible Causes

  1. Poor Internet Connection: A stable network is essential for sending emails. If your connection is weak or intermittent, messages will remain in the Outbox.

  2. Large Attachments: Emails with attachments exceeding the limit set by your email provider can cause messages to get stuck. Typically, attachment limits range from 10MB to 25MB.

  3. SMTP Configuration Errors: Incorrect outgoing server settings (SMTP) prevent Outlook from sending emails. Make sure these settings match those provided by your email service provider.

  4. Corrupted Outlook Profile: Sometimes the issue lies within your Outlook profile settings, which may require repair or recreation.

  5. Outdated Software: Outdated versions of Outlook or other related applications can introduce bugs that cause sending issues.

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Step-by-Step Troubleshooting Guide

Check Your Internet Connection

  1. Test Connectivity:

    • Open a web browser and try loading a page. If pages do not load, your internet connection may be down.
  2. Reconnect:

    • Restart your router or check with your Internet Service Provider (ISP) for outages.

Verify Outgoing Server Settings

  1. Access Email Settings:

    • Go to the File tab -> Account Settings -> Account Settings again -> Select the email account -> Change.
  2. Check SMTP Settings:

    • Ensure the outgoing server (SMTP) and the port settings match your ISP’s recommendations (common ports are 25, 587, or 465).
  3. Authentication Required:

    • Ensure “My outgoing server (SMTP) requires authentication” is checked.

Clear Your Outbox

  1. Remove Large Emails:

    • Open your Outbox and delete any emails that are too large. Consider compressing attachments before sending.
  2. Resend Problematic Messages:

    • If you have previously sent emails that remain stuck, try resending them or compose new messages.

Check for Pending Upgrades

  1. Update Outlook:

    • Go to the File tab -> Office Account -> Update Options -> Update Now to ensure you are running the latest version.
  2. Restart Outlook:

    • Sometimes simply closing and reopening Outlook can resolve sending issues after updates.

Repair Outlook Profile

  1. Open Control Panel:

    • Navigate to Control Panel -> Mail (Microsoft Outlook 16) -> Show Profiles.
  2. Create a New Profile:

    • Choose Add, then follow the prompts to create a new profile. Set it as default and reconfigure your email accounts.

Cause / Solution Table

CauseSolution
Poor internet connectionRestart router or check ISP status
Large attachmentsReduce size or remove attachments
Incorrect SMTP settingsVerify and correct outgoing server settings
Corrupted Outlook profileRepair or create a new profile
Outdated Outlook installationUpdate Outlook to the latest version
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Common Mistakes and How to Avoid Them

  • Neglecting Updates: Failing to regularly update Outlook can lead to compatibility issues. Make it a habit to check for updates monthly.

  • Ignoring Internet Quality: Assume that a connected status means a good connection. Perform regular tests to ensure signal strength is sufficient.

  • Overlooking Attachment Sizes: Regularly check the size of attachments before sending; compress files as needed.


Prevention Tips / Best Practices

  • Regular Maintenance: Periodically clear the Outlook cache to prevent corruption and issues with the Outbox.

  • Use Compression Tools: Tools like WinRAR or 7-Zip can help manage large attachments effectively.

  • Verify Settings Regularly: Periodically review your SMTP settings and configurations to prevent future issues.

  • Limit Check Frequency: Establish a schedule for sending and checking emails to avoid overwhelming the Outbox.


Frequently Asked Questions

How do I force Outlook to send an email stuck in the Outbox?

  1. Go to the File tab and select Options.
  2. Then under Advanced, enable Send immediately when connected.
  3. Click OK and try sending again.

Why is my email stuck in “queued”?

A “queued” email usually indicates that the email system will attempt to send it again later, often due to poor internet connectivity or issues with the email server.


Can I delete the .ost file to fix my Outbox?

Yes, you can delete the .ost file, but ensure Outlook is closed before doing so. The file will be recreated upon reopening Outlook.


What should I do if my SMTP is blocked?

If you suspect your SMTP is blocked, check with your ISP or hosting service for any connectivity issues. Additionally, check your server settings and test using another email client.

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Why isn’t my email sending despite an active connection?

The email client may be misconfigured, or there may be issues with the email account settings. Check all configurations thoroughly and ensure your account is in good standing.


In conclusion, when Outlook outbox doesn’t send messages, it can be attributed to various factors, including internet connectivity issues, large attachments, or incorrect settings that prevent efficient sending. Effective troubleshooting and preventive measures can help minimize occurrences of such frustrating issues in the future.

About the author

Jeffrey Collins

Jeffrey Collins

Jeffery Collins is a Microsoft Office specialist with over 15 years of experience in teaching, training, and business consulting. He has guided thousands of students and professionals in mastering Office applications such as Excel, Word, PowerPoint, and Outlook. From advanced Excel functions and VBA automation to professional Word formatting, data-driven PowerPoint presentations, and efficient email management in Outlook, Jeffery is passionate about making Office tools practical and accessible. On Softwers, he shares step-by-step guides, troubleshooting tips, and expert insights to help users unlock the full potential of Microsoft Office.