GainTools EML to MBOX Converter Review: Speed, Features & Pros

By Brandonswilliam     28-09-2026     6

Summary 

You might want to convert EML files to MBOX format if you want to move your emails from Windows Live Mail, Apple Mail or another program that supports EML over to an email client that uses the MBOX format. This is what GainTools EML to MBOX Converter is for, offering bulk EML processing, selective file selection, preview and local MBOX export.

In this review, we will look into its features, conversion workflow, considerations on speed, system requirements, and practical pros and cons.

Know about EML to MBOX Converter?

GainTools EML to MBOX Converter is a Windows application to convert EML files to MBOX. The product page says it can handle multiple EML files at the same time and supports EML files created by applications like Apple Mail, Windows Live Mail, Thunderbird and other email clients.

Current product version: 1.0 Compatibility: Windows 11/10/8.1/8/7 Installer size: 3.77 MB Trial version can convert 10 emails for evaluation purpose.

Key Characteristics


1. EML to MBOX Converter (Bulk)

Bulk migration is a significant feature. Now, instead of processing EML files one by one, users can select many files at once and export them into MBOX. This can be especially helpful if you have an email archive that has hundreds or thousands of individual EML files.

2. Selective EML Export

Rather than working with the whole collection, the application lets users choose separate EML files. If you want to migrate only some of the emails, this gives you more control.

3. Choose Folder or Individual File

GainTools offers two options to load EML data, one is to select a folder of EML files and other is to browse for individual files.

4. Preview before converting

You can preview the selected EML files in the application before exporting them. This allows the user to view the data selected before the MBOX output is generated.

5. Save MBOX on local drive

The transformed MBOX data can be saved to a destination selected on the local computer. The user can select an existing folder or create a new location for the output.

6. Retaining E-mail Data

The converter reads EML components like metadata, contacts, addresses, journals and notes during migration, GainTools says. The product page also says the conversion is meant to keep the original data.

7. No New Application Needed

The product page states that the converter does not require any additional software to run. This enables conversion to be done within the application itself rather than requiring the use of an alternative email client for the primary conversion process.

Speed & Performance Report

Speed is an issue when you are converting a large collection of EML. GainTools claims that the program provides simple and fast conversion assistance and supports bulk processing.

But the actual speed of conversion may vary depending on several factors:

  1. Count of EML files
  2. Size of single emails
  3. Attachment size
  4. RAM Available
  5. Performance of Storage Drive
  6. Overview of system architecture

The product page states the minimum requirements are 512 MB RAM, 1 GHz or faster processor and 100 MB free hard-disk space.

For a real performance test, the users should process their own representative EML dataset, because a small mailbox and a large archive can produce very different results.

How to Convert EML to MBOX: A Step-by-Step Guide

The conversion process is structured to follow a simple workflow.

1. Launch EML to MBOX Converter

Download the app to your Windows computer and run it.

Step 2: Choose EML Files

Select either File or Folder mode. You can browse to a specific EML file or a folder with multiple EML files.

Step 3: Preview the Chosen Data

Load the files and review the displayed EML data. It helps to make sure that the necessary emails are selected before the conversion.

Step 4: Choose MBOX as the Export Format

Select MBOX from the export options list.

Step 5: Select the Output Location

Choose destination folder to save the converted MBOX file.

Step 6: Run the Conversion

Click on Convert Now to start EML to MBOX conversion. After the process is finished, get the generated MBOX data from the selected location.

Who Can Use This Converter?

You can use the EML to MBOX Converter in many migration situations:

Windows Live Mail Users: Users with EML archives who want to import their messages into an MBOX compatible environment.

Thunderbird Users: Make ready EML data for Thunderbird's MBOX-based mailbox structure

Apple Mail Users: Need MBOX Output while working with EML data. GainTools specifically mentions the ability to export Apple Mail EML databases to Thunderbird MBOX.

IT Professionals: For large collections of individual EML files, administrators may use the folder and bulk-selection options to simplify processing.

Pros 

  1. EML to MBOX Converter
  2. Supports bulk EML to MBOX conversion
  3. Allows selective .eml file selection
  4. Allow folder based selection of EML
  5. Preview before you convert
  6. Data stored locally is converted
  7. Supports EML files from various email applications
  8. Does not require extra software
  9. Simple conversion process
  10. Supported on product page for Windows 11/10/8.1/8/7
     

Cons

  1. This product is currently only available for Windows and is not a native application for macOS/Linux.
    Free trial is limited to 10 email conversions.
  2. The real conversion speed is a function of the size and complexity of the EML dataset.
  3. If you have a very large archive, test the trial on a representative sample before doing a full migration.


Final Verdict

EML to MBOX Converter makes EML to MBOX migration easy with bulk processing, selective file selection, preview and local output saving. The folder selection can be useful, if EML files are stored in a nice folder hierarchy, and the bulk processing reduces the need for repeated one-by-one conversions.

The application has a pretty simple workflow for users who are planning to migrate from EML based archives to Thunderbird or any other MBOX compatible environment. You can also test the conversion process with the free trial before purchase.

FAQs
1. Does GainTools support conversion of multiple EML files to MBOX?

Yes The product supports multiple EML files exporting at the same time and bulk migration.

2. Can I choose individual EML files?

Yes, users can select single EML files or a folder containing EML data.

3. Can I convert Apple Mail EML files to Thunderbird MBOX format?

Yes. GainTools says Apple Mail EML database can be exported to Thunderbird MBOX.

4. Does the software require a second application?

The product page states that the converter doesn’t need any extra software to run.

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