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EML vs PST File Format

Let's look at the difference between EML and PST, two well-known email formats, and see how you can change one format to the other, if necessary.

Sooner or later, email users face the need to save one or more emails to a file for sharing with others or for backup. The question arises of which file format to use. The choice of the format for exporting messages depends on two main aspects:

  • which email client you use, and which client you will work with the emails later;
  • how many emails you need to save, one or several, or maybe the entire contents of a folder or a mailbox.

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 PST file format

PST is a Microsoft Outlook data file. It stores all information about the Outlook mailbox: messages, calendars, contacts, and other items.

PST is an internal Outlook format and cannot be opened or imported into other email applications.

PST data files are used for backups and archiving. You can store all mailbox data in them at once or selectively, segregating the files by type, date, or other attributes. Archived PST files are often created to organize messages or reduce the Outlook storage size.

What is the difference between EML and PST


  • The EML format is designed to store individual emails.
  • The PST format is used to store all Outlook mailbox data, including all item types, folder structure and settings.


  • EML files can be opened in almost any email application. Most email clients save individual messages in this format.
  • PST data files are Microsoft Outlook proprietary files and cannot be opened in other programs.


  • EML files are universal and can be opened in different operating systems and on different devices.
  • You need a Windows desktop or laptop computer to work with PST files.

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.
  • PST data file contains a complete copy of the entire mailbox or separate folders. It stores folder structure, rules, view settings, signatures, search folders, and other properties and settings, along with complete information about Outlook items.

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.

  • Since PST is Outlook's native format, it can be easily exported, viewed, and imported into the mailbox. You can use the built-in Outlook tools or special utilities with advanced settings to export or import PST files.

File sizes

  • EML files are bulky compared to other formats for storing individual messages, such as MSG for Outlook. This should be considered when backing up to cloud storage.
  • Since PST is a data file, it can be several tens of gigabytes in size, making it difficult or impossible to connect the file to the account. This problem is solved by splitting PST into smaller parts.

How to convert EML to PST

To work with EML emails in Outlook, you can import them into your mailbox. But sometimes, it is more convenient to change the single message format to the data file format, for example, when working with archives. To import EML to a PST data file, you need to use EML to PST converter software.

Professional EML to PST converter tool has extensive additional features:

  • Saves multiple EML files in one or more Outlook PST data files.
  • Imports EML messages to new or existing PST.
  • Transfers emails to a PST format with no changes, preserving all images, formatting, attachments, and Internet headers.
  • Divides PST by size, date, sender and recipient data or other parameters during conversion.
  • Maintains the original folder structure of EML files.
  • May move converted EML messages to another folder and mark them as unread in the resulting PST.
  • Can select EML emails for conversion: with or without attachments, no larger than a certain size.
  • Decodes Winmail.dat and other TNEF attachments.
  • The professional version of the utility uses the command line for mass EML to PST migration and scheduled conversion.
EML to PST Converter

How to convert PST to EML

To view Outlook messages from a backup or a mailbox data file in another mail client, you must convert the emails to one of the popular formats, such as EML. You won't be able to save messages from a PST data file in EML format using the built-in Outlook tools. Instead, you need to convert PST files to EML.

Advanced PST to EML converter has extra benefits:

  • Converts an unlimited number of PST files.
  • Saves all message data: headers, text with HTML markup, images, and attachments.
  • Preserves folder structure from PST files.
  • Creates new folders with EML files using macros, by message subject, sender or recipient data, dates and other properties.
  • Offers to choose the overwrite mode for duplicates at reconversion.
  • Uses filters when choosing messages to convert from a PST file: for a specified period, by days of the week and time of the day, received or sent only.
  • Performs mass PST to EML conversion and converts messages from PST to EML on schedule using the command line in the utility professional version.
PST to EML Converter


When choosing a format for storing and migrating emails, you must consider which email client you will work with the saved emails. The crucial factors are the number of messages and the email client to handle them.

Many users choose the popular EML format for storing separate emails to save a few messages. But if you are using MS Outlook, you cannot save mail in this format and can only view EML messages. Outlook uses its own data file format, PST, to store and migrate mail. A single PST file contains all messages and other items from a mailbox or folder.

You can migrate EML emails to an Outlook data file by importing EML into Outlook or after converting EML to PST. To view emails from your Outlook mailbox in other applications, you must export them to EML or convert Outlook emails from PST to EML format. The latter option is especially useful when retrieving messages from archived Outlook data files.

Other utilities are also helpful when working with EML and PST formats:

Check out our blog for detailed comparisons of other popular email formats: PST vs MBOX, EML vs MBOX, PST vs MSG, MSG vs MBOX, MSG vs EML.


How to mass change .eml to .pst?

The utility for converting from EML to PST allows you to change the format of an unlimited number of EML messages to PST. You can choose as many folders with EML files as you want. The command line app in the product's professional version helps perform bulk email migrations from different users' mailboxes.

How to add .eml files into an existing PST?

Professional EML to PST converter offers a choice between creating a new PST file or adding EML messages to an existing data file:

  1. Launch the utility.
  2. On the General tab, in the "Convert messages to PST data file" field, click the Select file or folder button and browse for the desired PST on your computer or drive.
  3. You can specify a new folder in the selected PST in the "Destination folder in PST file" field.
  4. Complete the other settings, if necessary, and click Run.

How to view messages from a PST file without Outlook?

The easiest way to extract messages from a PST file for viewing in applications other than Microsoft Outlook is to convert PST to EML format. The resulting EML messages can then be opened in almost any email viewer.

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