Outlook Error in Windows 10 Operating System

What is the Outlook error in Windows 10?

After upgrading to Windows 10, some users encounter an issue where the email client Outlook does not allow sending emails or emails get stuck in the Outbox folder. This disrupts daily work, especially when urgent communication is important. The disruption is often caused by configuration settings that changed during the system update, corrupted system files, outdated add-ins, or incorrectly interpreted server settings.
Below is a clear, step-by-step guide to help identify and resolve the cause of the error and restore smooth Outlook operation in the Windows 10 environment.

Why does Outlook not allow sending emails?

Sending issues in Outlook typically arise from the following reasons:

• Corrupted system files: after Windows 10 updates, essential system components may be damaged or not updated, affecting the performance of applications (including Outlook).
• Incorrect mail server settings: changes in the system environment may lead to inaccurate SMTP/IMAP/POP configurations (e.g., ports, encryption, authentication), causing sending issues.
• Software conflicts: incompatible Outlook add-ins, outdated antivirus or firewall, incorrect Work Offline settings.
• Stuck emails or large attachments: oversized attachments (e.g., >20 MB) or discrepancies in the mailbox can block sending.
• Changes in account data: if the password is changed on the service provider’s website, it must also be updated in the Outlook application.

How to fix the Outlook issue in Windows 10?

1. Close all Microsoft Office programs

Before starting diagnostics, close all open Microsoft Office programs and save documents to avoid data loss. Then press Windows logo key + X on your keyboard to open the administration menu.
Next, follow these steps:

1. Open the administrator console: select Windows Terminal (Admin) or Command Prompt (Admin) from the menu.
2. Run the System Image Repair (DISM): type DISM /Online /Cleanup-Image /RestoreHealth and wait for the process to complete.
3. Check system files (SFC): type sfc /scannow (make sure there is a space between „sfc” and „/”) and wait for the scan to reach 100%.
4. Check Outlook’s connection status: open Outlook and in the Send/Receive tab, ensure that Work Offline is not enabled.
5. Clear the Outbox folder: open stuck emails, remove oversized attachments or reduce their size; then try sending again.
6. Check account settings: ensure correct servers and ports (e.g., SMTP 587 with STARTTLS or 465 with SSL/TLS; IMAP 993; POP3 995), username, and password.
7. Run Outlook in Safe Mode: press Win + R, type outlook.exe /safe. If sending works, go to File > Options > Add-ins and disable problematic add-ins.
8. Repair Office installation: Control Panel > Programs and Features > Microsoft Office > Change > Quick Repair; if that doesn’t help – try Online Repair.
9. Recreate Outlook profile (if necessary): Control Panel > Mail (Outlook) > Show Profiles – create a new profile and set it as default.

How to prevent similar issues in the future?

To ensure that Outlook operates smoothly in the future, follow these recommendations:

• Regularly update the system and Office: install the latest Windows and Outlook/Office patches to avoid incompatibility.
• Periodically check the system: after major updates, run DISM /Online /Cleanup-Image /RestoreHealth and sfc /scannow to timely fix system discrepancies.
• Maintain account settings: after changing the password, update it in Outlook; regularly review SMTP/IMAP/POP, SSL/TLS, and authentication settings according to the service provider’s recommendations.
• Manage attachment sizes: limit large attachments or send links to file storage to prevent emails from getting stuck in the Outbox.
• Security and compatibility: use reliable antivirus, monitor firewall rules, and carefully assess the compatibility of add-ins.

By following these tips, you will reduce the risk of disruptions and maintain stable operation of Outlook and other Office applications even after significant Windows 10 updates.