The EML File Format

.Eml Email files represented as envelopes.

What is a EML file?

Files with the .EML file extension indicate the file is a formatted e-mail message. An EML file is created when an email message is saved in storage or forwarded using Outlook Express, Thunderbird, Windows Mail, or other email clients. It is also the format of a file that is created when a draft email message is saved to the hard disk.

The .eml file format is an open and published standard for exchanging email messages.

Many email clients have adopted the EML format, including as Windows Live Mail, Microsoft Outlook Express, Mozilla Thunderbird, IncrediMail and PST Viewer Pro for Windows users, and Microsoft Entourage and Apple Mail for Mac users. However, they can be opened by other applications as well. EML files are saved in the MIME RFC 822 standard format and are essentially text files, but they can also store attachments and hyperlinks which are encoded into the text of the file. When emails need to be archived, this is the type of file that is created.

The structure of an EML file includes a header and a body. The header stores information like email sender and recipient, the subject of the email, and the date and time at which it was sent. The body consists of the contents of the email. 


An EML file can sometimes be opened directly in a web browser, although doing so may cause some information in the email (such as header information, To, From, Subject fields, etc) not to be visible. To do this, just rename the “.eml” extension to “.mht”. Once this is done, the .eml file can just be double-clicked to open directly in your web browser. This is possible because the format of an EML file is very much like that of MIME HTML files. You can also open the file with a text editor (such as Windows Notepad) by renaming the file extension to “.txt”, but if the file contains attachments like images or hypertext, it will be in a coded format that is not readable. There are “base64” decoder programs available that will decode the attachment text that you’ll find in the EML file and display it in it’s intended format.


If you have Outlook Express but can’t open an EML file that has been sent to you, the following steps should correct the problem.

  1. Open the folder “My Computer”.
  2. Under the “Tools” menu select the “Folder options” item.
  3. Select the “File Types” tab.
  4. You will now see “Registered file” types where you can select “EML Outlook Express Mail Message”.
  5. Click “Advanced”.
  6. Click “Open” and then “Edit”.
  7. Enter the following line in the “Application used to perform action” box:
    “C:Program FilesOutlook ExpressMSIMN.EXE” /eml:%1
  8. Click OK in the following two dialog boxes and then close the window.
  9. You should now be able to open any EML file.

Before opening any EML file, remember to scan it with an antivirus program, as email messages can be infected with viruses. The Nimda worm creates EML files which are replicated throughout the infected system. However, even with the antivirus being active, there are some ISPs that automatically strip emails of EML attachments. If you see the message “<<MIME_ATTACHMENT_STRIPPED>>” at the end of the email, it means that there was an EML attachment that was blocked.


Unfortunately, Microsoft Outlook uses a proprietary .MSG Outlook message format which is not compatible with EML. MSG files cannot be opened by other email clients, although you can use a email viewer application like EML Viewer Pro to open .MSG files.

If you are an Outlook user, you can use the MessageExport add-in to save your Outlook email messages as EML files, as well as PDF and other formats.  


Download Eml Viewer

We hope this article has given you an understanding of what EML files are, how to create them and how to view them.

What Are EML Files?

Screen shot of PstViewer Pro email viewing and PDF software.

Files with the .eml extension are email files that store the content, headers, and pictures included in an email. They can also contain any email attachments, so the file size can be large.

In general, .eml files are created by Microsoft Outlook or other similar email programs when someone receives or saves an email. If someone has sent you a .eml file and you don’t have Outlook on your system, you can still open it through other programs, though.

You can easily open .eml files with Microsoft Outlook Express, Windows Mail, or Mozilla Thunderbird. On a Mac, Apple Mail is always included as a default program and will open .eml files, or the Microsoft program suite includes a version of Outlook that can open .eml files. Eml viewer software programs can process these files if its not desirable to install a full fledged email client application.

Another option for advanced users is to open the .eml files you receive with Internet Explorer, Opera, or another web browser. The compatibility varies depending on the browser software and version you have, the content of the email and so on, but if you’re desperate for another option, this might work. If you can’t figure out how to do this, you can change the file extension from .eml to .mht and it may work. EML and MHT files are very similar, except that MHT files do not have the email header information. For some people, understanding how to change a file extension may be difficult, and it may be impossible if you are operating from a Windows account without Administrator privileges.
While the average .eml file should be accessible through an e-mail application or web browser, if this doesn’t work you could try to email the sender of the .eml file and ask them to forward the original email to you as text instead.
If you have many .EML files that you need to search or process, you can try a .EML file viewer.  PST Viewer Pro is one such viewer that is able to work with many different file types such as .EML, .MSG, .PST, .OST and even .MHT files.  Click here for more information on PST Viewer Pro and to download a free trial.
Review the specification for RFC 2822, Internet Messaging standard. or read “What Is .EML” for more information on .eml documents.