EML is a file extension for an e-mail message saved to a file in the MIME RFC 822 standard. It was introduced by Microsoft in their classic Outlook Express email program.

EML files can contain plain ASCII text for the headers and the main message body as well as hyperlinks and attachments.

MIME stands for Multipurpose Internet Mail Extensions. It extends the basic email format, allowing it to store data in character set other than ASCII, and other email data, such as audio, video, images, and application program files as attachments.

The files with the .eml extension can be opened directly with any text editor. This gives the user direct access to the headers, the message body, and the attachments. This is usually enough to review plain text messages. However, things get more complicated when the messages include CSS, HTML, and attachments. The attachments are using base64 encoding which adds big blocks of text for the attached files. EML files which include HTML and attachments are usually harder to understand and a viewer might come in handy.

The Outlook Express application is long gone. Currently, the EML files are mostly associated with the Thunderbird free email application. This is the default format for exporting messages from Thunderbird. This is also the format if you try to forward a message as an attachment in this email programE.

If you don’t have Mozilla Thunderbird installed, you can use the MsgEml.com site to view such messages directly. Locate the particular .eml file via the file upload form and submit it for processing. Then it will be displayed in your browser.

Other places where you can run into email data in MIME format is the mail folder in the root of the cPanel control panel. This is where the raw data of the cPanel-managed email boxes is stored. The messages there are stored in files with long, ugly names, but the format is the same. You can open these files in the cPanel file manager, copy the text, and paste it in the text field of MsgEml.com.