Why Are MSG and EML Files Not Opening? Causes, Fixes & Best Solutions

MSG and EML are two of the most commonly used email file formats for storing individual email messages. While MSG files are primarily associated with Microsoft Outlook, EML files are supported by several email clients, including Windows Mail, Thunderbird, Apple Mail, and others. Despite their popularity, many users encounter a frustrating issue where these email files simply refuse to open.

If you are unsure about the differences between these formats, read our detailed guide on MSG vs EML before troubleshooting the issue.

You may double-click an MSG or EML file only to receive an error message, see a blank email, or find that no application is available to open it. In some cases, attachments are missing, formatting is broken, or the file appears to be corrupted even though it was working earlier.

This problem can occur due to missing email clients, file corruption, incorrect file associations, compatibility issues, damaged storage media, or unsupported email formats. Fortunately, most of these issues can be resolved with a few troubleshooting steps.

In this guide, we’ll explore the most common reasons why MSG and EML files fail to open, along with practical solutions to help you access your emails without losing important data.

What Are MSG and EML Files?

Before troubleshooting the issue, it’s helpful to understand the difference between these two email file formats.

MSG File

An MSG file is a proprietary email format created by Microsoft Outlook. It stores –

• Email content
• Subject
• Sender and recipient details
• Attachments
• Calendar items
• Contacts
• Email metadata

Because it is Outlook-specific, opening an MSG file usually requires Microsoft Outlook or compatible software.

EML File

EML is a standard email format supported by multiple email clients. An EML file stores –

• Email body
• Attachments
• HTML formatting
• Sender information
• Recipient information
• MIME encoding
• Date and time

Unlike MSG, EML files are more widely supported across different platforms.

Why Are MSG and EML Files Not Opening?

Several technical reasons can prevent email files from opening correctly. The most common causes include –

• Microsoft Outlook is not installed
• Windows Mail is unavailable
• Incorrect default application
• Corrupted email files
• Unsupported Outlook version
• Damaged file headers

• Incomplete email download
• Broken MIME encoding
• Virus infection
• File permission issues
• Email client incompatibility

Let’s examine each solution in detail.

Fix 1 – Check Whether the Required Email Client Is Installed

This is the most common reason behind the problem.

MSG files generally require Microsoft Outlook.

EML files typically require –

• Windows Mail
• Thunderbird
• Apple Mail
• Outlook
• Other compatible email applications

If no compatible email client is installed, Windows or macOS cannot determine how to open the file.

Install a supported email application before attempting to open the file again.

Fix 2 – Verify the Default Application

Sometimes the correct software is installed but isn’t associated with MSG or EML files. To fix this –

• Right-click the email file.
• Select Open With.
• Choose the appropriate email client.
• Enable Always use this app.

This updates the file association and prevents future opening errors.

Fix 3 – Check If the File Is Corrupted

A corrupted email file may display errors such as –

• File cannot be opened.
• Invalid file format.
• Unsupported message.
• Cannot read message.
• Unknown error occurred.

Common reasons for corruption include –

• Interrupted downloads
• Disk failures
• Malware attacks
• Improper file transfers
• Unexpected system shutdowns

If the original source is available, download or export the email again.

Sometimes corrupted email files also experience formatting or encoding problems. Learn how to fix common EML file encoding issues before attempting another conversion.

Fix 4 – Confirm the File Extension

Many users accidentally rename email files. For example –

invoice.msg.txt

meeting.eml.docx

email.msg.pdf

Although these filenames appear correct, the actual file format has changed.

Enable file extensions in your operating system and verify that the file ends with –

.msg

.eml

Incorrect extensions prevent the operating system from recognizing the email format.

Fix 5 – Look for Incomplete Downloads

If an email file was downloaded from cloud storage or received as an attachment, it may not have downloaded completely. Signs include –

• Very small file size
• Blank email
• Missing attachments
• Unexpected opening errors
• Download the file again using a stable internet connection.

If downloaded EML files are missing embedded files or documents, read our guide on EML attachments not showing.

Fix 6 – Update Microsoft Outlook

Older Outlook versions sometimes fail to open MSG files created by newer releases. Similarly, outdated email applications may struggle with modern EML formatting. Updating your email client can resolve compatibility issues and improve support for newer file structures.

Fix 7 – Check File Permissions

Sometimes Windows blocks files downloaded from the internet. To verify –

• Right-click the file.
• Select Properties.
• Click Unblock (if available).
• Apply changes.

Then try opening the file again.

Fix 8 – Scan for Malware

Malicious software can damage email files or prevent them from opening correctly. Run a complete antivirus scan if –

• Multiple email files suddenly stop opening.
• Attachments disappear unexpectedly.
• The file size changes without explanation.

Removing malware may restore normal file access if the files themselves remain intact.

Fix 9 – Test the File on Another Computer

If the email still won’t open, copy it to another Windows or Mac system. If it opens successfully elsewhere, the problem is likely related to –

• Installed applications
• Operating system settings
• File associations
• Local software conflicts

This simple test helps determine whether the issue lies with the file or your computer.

Fix 10 – Check Large Attachments and Encoding Issues

Some MSG and EML files contain large attachments, embedded images, or complex HTML formatting. If the email client doesn’t fully support these elements, the file may open incorrectly or appear blank.

In addition, encoding problems—such as damaged MIME headers or unsupported character sets—can cause email content to display as unreadable symbols or missing text.

If you notice broken formatting, missing images, or strange characters, the issue may be related to compatibility rather than actual file corruption.

When Manual Fixes Don’t Work

If you have tried all the above troubleshooting methods and your MSG or EML files still won’t open, the issue may involve deeper file corruption, compatibility limitations, or damaged email structures that standard email clients cannot handle.

Instead of spending hours trying different applications, using a dedicated email conversion tool can be a practical solution. Professional software can read inaccessible email files, preserve their contents, and convert them into formats that are easier to access across different platforms and email clients.

Use a Professional Solution to Open Inaccessible MSG and EML Files

When manual troubleshooting fails, the problem is often more complex than a simple software or settings issue. Email files may be partially corrupted, incompatible with your current email client, or created using a different application version. In such situations, professional email conversion software provides a more reliable way to access your data.

Whether you’re dealing with an Outlook MSG file or an EML file from another email client, MacMister offers dedicated tools to help you open, convert, and preserve your email data without affecting its integrity.

Solution 1 – Open MSG Files with MacMister MSG Converter

If your MSG files won’t open because Microsoft Outlook isn’t installed or the files are incompatible with your current Outlook version, MacMister MSG Converter for Mac can help.

The software reads MSG files directly and converts them into multiple formats, making them accessible across different email clients and platforms.

Steps to Convert MSG Files

Step 1 – Install and launch the MacMister MSG Converter on your Mac.

Step 2 – Click Add Files or Add Folder to import your MSG files.

Step 3 – Preview the loaded emails and choose the required folders.

Step 4 – Select your preferred output format such as PDF, PST, EML, MBOX, HTML, or Office 365.

Step 5 – Choose the destination location and click Convert.

Within a few minutes, your inaccessible MSG files are converted into a format that you can easily access.

Solution 2 – Open EML Files with MacMister EML Converter

If EML files fail to open due to unsupported applications, damaged file associations, or compatibility issues, MacMister EML Converter for Mac offers a simple solution.

The software converts EML files into multiple formats while preserving every email property.

Steps to Convert EML Files

Step 1 – Launch the MacMister EML Converter.

Step 2 – Add individual EML files or an entire folder.

Step 3 – Preview emails before conversion.

Step 4 – Select the desired export option, including PST, PDF, MSG, MBOX, HTML, Gmail, or Office 365.

Step 5 – Click Convert to begin the process.

Once completed, your EML files become accessible in the selected format without losing attachments or formatting.

Why Choose the Email Converters?

Both MacMister tools are designed to simplify email management while maintaining complete data integrity.

Key Features

• Supports bulk email conversion.
• Preserves original folder hierarchy.
• Maintains attachments and inline images.
• Retains email metadata (To, From, Subject, Date).
• Keeps HTML formatting intact.
• Provides preview before conversion.
• Supports selective conversion using filters.
• Exports to multiple file formats.
• User-friendly interface.
• Compatible with the latest macOS versions.

These features make the tools suitable for both individual users and IT professionals handling large email archives. If you need printable copies of important emails, you can also convert MSG files to PDF or save EML files as PDF while preserving formatting.

Additional Tips to Avoid MSG and EML File Issues

To reduce the chances of file opening errors in the future –

• Always keep a backup of important email files.
• Avoid renaming file extensions manually.
• Update your email client regularly.
• Use trusted sources when downloading email attachments.
• Store email files on healthy storage devices.
• Scan downloaded files for malware.
• Avoid interrupting file transfers.
• Verify file integrity after copying between devices.
• Use compatible email applications for viewing files.
• Convert email files to widely supported formats when sharing them with others.

Following these practices can help prevent common compatibility and corruption issues.

Conclusion

MSG and EML files may fail to open for several reasons, including missing email clients, incorrect file associations, corrupted files, compatibility issues, damaged downloads, or unsupported email formats. Fortunately, many of these problems can be resolved by checking your software configuration, updating applications, verifying file integrity, and correcting system settings.

However, when manual methods don’t work, professional conversion software provides a faster and more dependable solution. The MSG Converter enables you to access Outlook MSG files by converting them into multiple formats, while MacMister EML Converter performs the same task for EML files without affecting attachments, formatting, or metadata. Using the right tool ensures that your important emails remain accessible regardless of the email client or platform you are using.