Solve OST File Opening by Converting OST Emails into MHTML

Outlook is an email client that helps users with email communication. It is a major part of day-to-day communication. It stores its data in OST (Offline Storage Table). An OST file stores a local copy of Outlook data and allows you to work offline. However, when Outlook fails to open, it will affect the OST files. Whenever Outlook fails to open an OST file, it becomes orphaned, and the user can’t open or read it. Since OST files depend on Outlook to load, any issue with Outlook directly affects your ability to view your mailbox. It can block your entire workflow, especially when important emails or attachments are urgently required.

Don’t need to panic, you can still access all your mailbox data, even if Outlook is not opening it. In this case, users can convert the OST file into a browser-friendly format like MHTML or HTML format. After conversion, users can open their data in a web browser like Chrome, Edge, or Firefox.

This blog explains why Outlook stops opening OST files, why MHTML is a better format, and how you can convert OST files to MHTML effortlessly.

Why Outlook Fails to Open OST Files

Before looking at file formats, it’s important to know why Outlook suddenly stops opening OST data. Common reasons include:

• A corrupted OST File can prevent Outlook from opening your account, leading to the program freezing or displaying multiple error messages.
• The Broken Outlook Profile will stop Outlook from launching and loading the associated Outlook profile.
• Outlook running in the background could prevent the launch of new Outlook sessions, as Outlook may not have shut down properly before.
• Corrupted Windows System Files could prevent Outlook from opening properly as well.

These problems cause interruptions in your work and make your mailbox inaccessible.

HTML vs MHTML – Which Format Should You Choose?

Both HTML and MHTML formats open easily in any browser, but they work differently.

• HTML Format: HTML stores only the main page structure. Images, styles, and scripts are stored separately in different folders. This means email formatting may not appear perfectly unless all supporting files are present.
• MHTML Format: MHTML stores the entire webpage—HTML + images + CSS + inline content + attachments—inside a single file.

In Simple Words:

HTML → Good for basic content only

MHTML → Best for full email preview and one-file storage

For users who want accuracy, readability, and quick access, MHTML is the superior choice.

How to Convert OST to MHTML Format

You can convert an OST file to MHTML in two ways: manually or using a converter tool.

Manual Method (Works Only If Outlook Is Open)

Outlook only allows for email export to MHTML format using the built-in Export function. You must have access to an uncorrupted OST file for this method of exporting emails from Outlook to be successful. If Outlook does not open, the Export function is ineffective because it requires Outlook to be open.

To convert one email from Outlook to MHTML, follow these steps:

• Start Outlook and ensure you can access your OST file.
• Locate the individual email you wish to convert.
• Select File on the menu bar and then click Save As from the drop-down menu.
• In the Save As dialog box, select MHT/MHTML as the file type.
• Navigate to where you want to save your MHTML file and select Save.

You can open the created MHTML in any internet browser (such as Chrome, Edge, or Firefox).

Limitations of the Manual Method

The manual method has several restrictions, and it cannot convert the entire OST file. Here are the major limitations

• Cannot convert the entire OST file
• Requires Outlook to be working
• Very slow for large mailboxes
• Formatting or images may break
• Not suitable for thousands of emails

Because of these drawbacks, the manual method is suitable only for very small or occasional email exports, not for complete OST-to-MHTML conversion.

Professional Method: Convert OST to MHTML

If your OST file is inaccessible or Outlook refuses to open, the WholeClear OST to MHTML Converter is the most effective solution.

This tool directly reads orphaned, damaged, or inaccessible OST files and converts them into clean MHTML files—without requiring Outlook or Exchange Server.

Key Benefits of using OST to MHTML Converter

• Converts complete OST files to MHTML with accuracy
• Opens corrupted or orphaned OST files
• Preserves folder hierarchy, formatting, inline images, and attachments
• Supports bulk OST file conversion
• No Outlook installation is required
• 100% safe and quick process

Steps to Convert OST to MHTML Using the Professional Tool

1. Install and launch the WholeClear OST to MHTML Converter on your computer.
2. Select your OST file by clicking the Add File / Add Folder button.
3. This will allow the software to scan and display all of your Outlook folders in a tree-like structure.
4. Select the folders or emails you want converted.
5. Specify MHTML as the output format.
6. Select where you would like to save the converted files.
7. Click the Convert button to start the conversion process.

After the conversion is complete, open the folder that contains the converted files, and you can immediately view your mailbox information in any browser.

Conclusion

When Outlook won’t open anymore, this affects not only your entire workflow but also renders your OST file unworkable. Don’t waste your time trying all kinds of repair techniques, nor do you need to panic about the idea of losing emails. The solution to both these problems lies in converting the OST file to MHTML.

MHTML maintains the structure, attachments, and format of your email in a single file that can be opened easily.

The WholeClear OST to MHTML Converter allows you to access your OST file data without using Outlook in a smooth, quick, and reliable manner. Whether your file is damaged or Outlook is not functioning, you can still view your mailbox at any time directly from your web browser.