Send & Receive Issues

How to Fix Outlook Mail System Failure When Sending Excel Attachments

Amos Gikunda Oct 9, 2026 868 views

Question details

The user is unable to email a spreadsheet directly from Excel and encounters a mail installation error.

How to Fix Outlook Mail System Failure When Sending Excel Attachments

Product: Microsoft Excel / Outlook
Device & OS: Windows
Scenario: Attempting to use the 'Send to Mail recipient' feature in Excel to attach and send a spreadsheet via Outlook.
Observed behavior: The system throws a 'Mail system failure. Check your mail installation' error, preventing the Excel file from being attached to an email.

Before you start

Ensure that you have administrative privileges on your Windows computer, as modifying default system applications and running Office repairs require admin rights. Save and close all active Excel workbooks before beginning.

Solution 1Recommended

Set Outlook as the Default Email Application

Configuring Windows to recognize Outlook as the primary mail client resolves communication errors between Excel and the email system.

Excel relies on the Windows operating system to identify which program should handle email requests. If this registry setting is missing or pointing to a different app, the attachment process will fail.

Open Windows Settings

Click the Windows Start button, type 'Default apps' in the search bar, and press Enter to open the Default apps settings menu.

Locate Email Settings

Scroll through the list of default applications until you find the 'Email' category.

Select Microsoft Outlook

Click on the currently listed application (or the '+' icon if none is selected) and choose 'Outlook' from the drop-down list.

Set Outlook as the Default Email Application

Refresh Settings: If Outlook is already selected, try switching it to another app (like Windows Mail) temporarily, then switch it back to Outlook to refresh the system registry.

Solution 2

Run an Online Repair for Microsoft Office

If setting the default app doesn't work, the Office installation files may be corrupted and require a system repair.

Free Microsoft Office alternative

Try WPS Office for Seamless Email Integration and File Sharing

If Microsoft Office continues to experience registry errors or installation failures, consider switching to WPS Office. It provides a lightweight, hassle-free environment that seamlessly integrates with default email clients, allowing you to share spreadsheets without complex troubleshooting.

1. Install WPS Office: Download and install the free version of WPS Office on your Windows PC.
2. Open Your Spreadsheet: Launch WPS Spreadsheets and open your existing Excel workbook.
3. Share via Email: Click 'Menu' in the top-left corner, go to 'Share', and select 'Email' to instantly attach the file to your default mail client.

Fully compatible with Microsoft Excel formats (.xlsx, .xls, .csv).Built-in one-click email sharing without relying on complex system registries.Lightweight installation that takes up minimal system resources.Familiar user interface with zero learning curve for former Office users.

microsoft office alternative - wps office

Frequently Asked Questions

Why does Excel show a 'Mail system failure' even when Outlook is open?

This happens when the Windows registry loses the specific MAPI (Messaging Application Programming Interface) connection identifying Outlook as the default email client, which can happen even if the Outlook program is currently running in the background.

Will repairing Microsoft Office delete my files or emails?

No. Running a Quick Repair or Online Repair from the Control Panel only replaces corrupted program files and settings. It will not delete your personal documents, saved spreadsheets, or Outlook data files (.pst/.ost).

Can I send an Excel attachment without fixing this error?

Yes. As a workaround, you can simply save your Excel spreadsheet to your computer, manually open Outlook (or your preferred webmail), compose a new email, and use the 'Attach File' button to add the spreadsheet.

Outlook & Email Problems