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EML vs MBOX File Format

This article will look at the two most common formats for saving single emails or an entire mailbox folder in separate files. Let's see what the difference is between EML and MBOX and how to change one format to the other.

Email is a means of transmitting information in the form of messages. Email messages can be saved in files to your computer, external drive, or cloud storage like any other data.

There are several file formats for saving individual emails or the entire mailbox contents. These email file formats vary not only in content, but also in the email program you use.

What is the EML message format

The EML is a very common format for saving and transferring individual email messages between different email systems. Many, such as Mozilla Thunderbird, Windows Mail, Apple Mail, Outlook Express, etc., use this format to save emails. Others can import or open EML files without additional tools.

Most email applications can open EML files for viewing. EML files can also be opened in a text editor.

A single .eml file can contain only one message with all of its contents, including formatting, images, and attachments.

What is the MBOX file format

MBOX is a data file format for storing all messages from a mailbox or folder. It is one of the most popular formats for storing email message databases.

Many email clients such as Mozilla Thunderbird, Mac / Apple Mail, Eudora, and others use the MBOX file in their work. Other applications, such as Gmail, use this format only for backing up and exporting messages.

The MBOX format allows you to store all emails from a mailbox folder in a single file. In this text file, messages are stored in chronological order, one after the other. To view them separately, you must convert MBOX to a different format.

What is the difference between EML and MBOX


  • The EML format is designed to store individual emails.
  • The MBOX format is used to store and back up email databases.


  • EML files can be opened in almost any email application. Most email clients save individual messages in this format.
  • Many email clients use the MBOX format to store and migrate data.


  • EML files are universal and can be opened in different operating systems and on different devices.
  • You can save the MBOX file on different media or in the cloud and transfer it to another computer running Windows or Mac OS. Since it is a text format, files with an .mbox extension sometimes can be partially viewed with a text editor, such as Microsoft Word or Notepad.

File contents

  • EML files contain most of the message data, including attachments, but, for example, some internal Outlook properties and fields cannot be saved in EML format.
  • An MBOX file stores the messages in EML format with all the data, including attachments. But, although MBOX is designed to store multiple messages, it cannot store the folder structure. Each MBOX file contains messages from a separate mail folder.

Working with files in Outlook

  • An EML file can be opened with Outlook. If you have Microsoft Outlook installed, just double-click the file with the .eml extension to open it. When you drag and drop an EML file into an Outlook Inbox folder, a new message is created, and the file is added as an attachment.
  • You can use a special tool to export Outlook messages to EML files.

  • Outlook uses its own PST format to work with message databases. MBOX data files cannot be opened or transferred to Outlook without third-party tools such as Import messages from MBOX to Outlook or Convert MBOX to PST.

File sizes

How to convert MBOX to EML

MBOX is a single file that contains many messages. If you need to view or share one or more emails from this data file, you cannot extract them manually. You must use a special solution for MBOX to EML conversion.

The advanced version of MBOX to EML converter allows you to:

  • Convert multiple MBOX files simultaneously.
  • Preserve folder structure when converting MBOX files from multiple subfolders.
  • Transfer messages from MBOX to EML, retaining the formatting, attachments, headers and other information.
  • Choose options for existing EML files to avoid duplication or data loss.
  • Use the command line to migrate multiple mailboxes of different users and create other mail migration scenarios.

Once MBOX files are divided into separate EML messages, they can be handled in Windows Explorer, transferred to other users, and imported into Outlook and other mail applications.

MBOX to EML Converter


As you can see from the EML vs MBOX comparison, both formats are universal and are supported by different email clients. They are widely used for backups, transferring emails to other mailboxes and exchanging information between users.

The main difference between EML and MBOX formats is that EML stores individual messages in each file separately, while MBOX stores multiple messages in a single file. You can extract individual EML messages from a common MBOX file with MBOX to EML converter.

Both of these formats are not Microsoft Outlook files. You need to use the special tools in this article to export messages from EML and MBOX to Outlook.

You can use other tools to work with EML and MBOX files:

Microsoft Outlook uses two similar formats, MSG and PST, to store messages and other items individually or together. See also comparisons of other mail formats:


How do I transfer saved EML messages to an MBOX file?

If you have Microsoft Outlook installed, you can use special add-ons:

  1. Convert EML messages to MSG format, and then convert MSG to MBOX.
  2. Transfer the desired EML files into a single PST data file, and then convert PST to MBOX.

All the original information is saved during the conversion with no changes or losses.

Do MBOX files contain attachments from original messages?

Yes, MBOX files store your messages practically as they were received. Thanks to the MIME data encoding method, MBOX preserves not only text but also images and attachments.

How do I export Gmail messages to EML and MBOX files?

Read our blog about exporting Gmail messages to learn how to save Gmail mail in different formats.

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