Quick & Easy Solution to Convert OST to EML Format

Written By Lovely Baghel
Published on: July 30th, 2025

When using Exchange, IMAP, and Office 365 accounts with Microsoft Outlook, mailbox data is stored in *.ost (Offline Storage Table) files. You won’t be able to view those emails unless you use Outlook or Exchange, or convert OST to EML. EML files are single-message email files by Thunderbird, Windows Mail, Apple Mail, etc. In this article, look at the best manual method and the SysInfo OST to PST Converter to change format easily, without losing attachments or metadata.

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There are many reasons for OST to EML conversion, whether it is for archiving purposes, legal compliance, or changing email platforms. Using EML instead of your OST file will improve portability, accessibility, and compatibility.

Why Users Prefer to Convert OST File to EML?

Before getting into how, it is helpful to know some of the different advantages of using EML over OST in specific situations:

EML can be opened in many different email clients. Say, Thunderbird, eM Client, Apple Mail, etc. Whereas, OST files are tied to Outlook.
EML is a standard file that makes parsing emails easier. So the forensics, legal, and audit teams prefer EML files over actual email clients. Because the latter can sometimes be more difficult to navigate and handle.
An EML file contains one email, which makes it easier to extract, classify, and index emails. On the other hand, you cannot do this with an OST file.
You cannot access an OST file without Outlook and a synced profile, while an EML is a stand-alone file.

How Can You Quickly Convert OST to EML?

The methods that we are going to discuss here are quite straightforward. The first one is a manual method, but it requires multiple limitations and can be complex, especially for new users. The other method is with the use of an automated utility, which is very simple and easy to use for everyone and runs on all OS environments.

Traditional Approach to Export OST to EML

Remember that it only works for the Windows OS. And you need Outlook, Gmail, and other desktop email clients like Thunderbird or WLM for this. Also, three more prerequisites must be fulfilled:

The OST file should be accessible via a configured and active MS Outlook profile.
Installation of Mozilla Thunderbird (or a similar EML-supportive email client).
An IMAP-enabled Gmail account for configuration with other applications.

Now, to convert OST to EML, follow these steps:

First, sync the Gmail account and Outlook profile via IMAP.(Use the Add Account option)
After that, import your .ost files into the synced Gmail folder. (Via drag & drop or the Import/Export wizard)
Then, start Mozilla Thunderbird and again process the configuration.
Connect the same Gmail and Thunderbird accounts and restart it.
Further, select all the emails in the Gmail inbox with Ctrl + A.
For selective conversion, select only the needed emails and right-click.
Later, click Save As, and a new dialog opens where you need to pick a folder.
Finally, click Select Folder, and all the selected emails are saved as EML files.

Note: Another alternative that you can use to convert OST file into EML is by:

Follow the same steps from 1-6 as mentioned above.
Then, select Export Messages As from the Thunderbird options.

(You need to have the ImportExportTools NG add-on extension added in your profile beforehand for this option to appear.)

Afterward, select EML Message Format and pick with Attachments.
Lastly, press Select Folder after choosing one to finish saving files as EML.

Shortfalls of the Manual Method

Tedious when doing mass conversion.
Need Outlook and another 3rd party email client.
May not retain attachments and formatting accurately.
Cannot process orphaned files or corrupted OST files.
Lengthy with lots of steps one after the other and need of internet.

Proficient Tool Solution to Convert OST to EML

If you are dealing with inaccessibility or oversized OST files, or you need bulk conversion with attachments, metadata, and folder structure retained. Utilize a professional OST to PST Converter Tool that is used by IT teams and migration specialists to load OST files. It also gives you the ability to preview your mailbox data before conversion.

Additionally, you can easily select just the emails or all emails, and export to .eml format. Moreover, it also helps you retain the attachments and folder hierarchy as is. Besides that, you can convert bulk OST files at one time, again with no dependency on Outlook.

“An IT administrator was responsible for managing compliance audits. He needed to extract and preserve mailbox data from multiple people who had terminated employment. Their Exchange profiles were inactive, and the OST files were orphaned as the email users. Using the best OST to EML Conversion Tool, he was able to extract 10,000+ emails into EML format in only a few hours and submit them for legal review.”

Procedural Guide for Users to Convert OST File to EML

Start the tool: OST File Exporter and add your OST files to it.
Afterward, click Next and proceed to the preview pane.
Verify and check the folder structure and attachments, and pick them.
Later, click Next and again select the .eml format for the output.
Then, choose your filters as per the need and set a preferable location.
At last, complete your OST file to EML conversion process via Convert.

Explore More: Import NST File to Outlook

Conclusion

When you convert OST to EML, you get the flexibility to access Outlook emails across different platforms without Exchange, IMAP, or Outlook. The manual method works for small, healthy, and active OST mailboxes. But for all your large conversion needs with inactive OST files and big attachments, the expert tool is an excellent choice. Download the demo version of this tool for a try and functionality check, and if you face difficulties, get in touch with our chat support.

Frequently Asked Questions

Q. Can I manually export OST emails to EML format?

Ans: Yes. You can manually export OST to EML the long way. Use the following steps:
1. Configure Gmail and Outlook accounts.
2. Then, add OST emails to the Gmail account.
3. Configure the same Gmail account with a Thunderbird profile.
4. Lastly, use Save As or ImportExportTools NG to change to EML.

Q. Is it possible to convert corrupted OST files to EML?

Ans: No, you cannot directly convert corrupted OSTs to EML. You need to first repair them with the OST Recovery, and then you can save them as EML without difficulties.

3. Can I convert multiple OST files into EML in one go?

Ans: Yes, of course. The professional tool above, i.e., OST to EML Exporter, allows you to batch convert OST file into EML at once. You need not worry about size restrictions or the number of files you add to the tool.

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About The Author:

Lovely Baghel

As a content writer, I specialize in Email Migration, Data Recovery, Email Backup, and File Management. I have been writing professionally for two years now. There is so much information available in this field that I am intrigued by the newer technologies and techniques.