What is an EML File and What is Inside It?
EML is the file extension for one saved email message. The file contains the headers, the body, embedded images and attachments of that message.
Email programs create these files when you save a message or drag it out of the inbox. Many people meet the format when a support team asks for the original message.
| Detail | EML |
|---|---|
| Extension | .eml |
| Contents | One email message with headers, body and attachments |
| Standard | Internet Message Format (RFC 5322) with MIME parts |
| MIME type | message/rfc822 |
| File kind | Plain text with encoded attachments inside |
How is the Format Built Inside?
An EML file is plain text. Header lines come first, then a blank line, then the message body.
- Headers. Lines like From, To, Subject, Date and Received name the sender, the route and the time.
- Body. The text or HTML version of the message sits below the headers.
- Attachments. MIME splits the message into parts. Files travel as encoded text, base64.
Microsoft Outlook, Thunderbird and Apple Mail all know this layout, so one message file moves between them without a converter.
Do You Know? EML has no fixed signature bytes. Tools identify it from the header lines at the top.
How do You Open an EML File?
Double click the file first. Windows opens it in the mail program that owns the .eml extension.
Method #1: Open in Outlook (Free With Outlook)
Who it suits. Windows users with Outlook installed. Extra application. None.
- Right click the message file in File Explorer.
- Select Open with and then Outlook. In new Outlook, choose Outlook (new).
- Close the message window when you finish. The file stays on the disk.
Drag the file onto the reading pane in new Outlook. Microsoft explains the drag and drop steps for new Outlook and Outlook on the web.
Method #2: Open in Thunderbird or Apple Mail (Free)
Who it suits. Users without Outlook. Extra application. Thunderbird on Windows and Linux or Apple Mail on Mac.
- Right click the file and select Open with.
- Select Thunderbird on Windows or Linux. Select Mail on a Mac.
- Read the message and save attachments from the attachment bar.
The read EML files without Thunderbird thread lists more viewers for people who have no mail program.
Method #3: Open in a Text Editor (Free)
Who it suits. Admins who check headers. Extra application. Notepad.
- Right click the file and select Open with and then Notepad.
- Find the Subject, From and Received lines at the top.
- Close the file without saving, because a text editor can damage the encoded attachment parts.
Heads Up. A text editor shows raw code, so images and formatting do not appear. Use a mail program for a normal view.
Is It Safe to Open EML Attachments?
The EML format itself holds text, but attachments inside can carry malware. Open them only from senders you know.
Scan attachments with your antivirus program before you open them. Avoid links in the body until you trust the sender.
How is EML Different From MSG?
EML is an open standard that most mail programs understand. MSG is a Microsoft format built for Outlook.
| Point | EML | MSG |
|---|---|---|
| Format | Plain text, RFC 5322 and MIME | Binary, Compound File format from Microsoft |
| Programs | Outlook, Thunderbird, Apple Mail and more | Outlook and tools built for MAPI |
| Contents | One email message | Email, contact, appointment or task |
| Strength | Moving mail between programs | Outlook specific data |
Our MSG file extension guide explains the Outlook format in detail.
How do You Convert or Move These Messages?
Choose the target first. Every target has its own guide on this site.
- Convert EML files to MSG for Outlook specific storage
- Convert EML to PST manually when you need one Outlook data file
- Convert multiple EML files to PDF for sharing and records
- Import EML files into Outlook for mailbox use
- EML to Microsoft 365 for cloud mailboxes
Test the result on a small batch before you convert thousands of files.
Frequently Asked Questions
What does EML Stand for?
EML is the file extension for an email message. Many people read EML as email. The RFC does not define a longer name.
Can You Open EML Without Outlook?
Yes. Thunderbird, Apple Mail and Windows Mail open them. A text editor opens the raw message with headers and encoded attachments.
Are Attachments Stored Inside EML?
Yes. MIME packs attachments inside the file as encoded text. A mail program decodes them when you open the message.
Can You Edit EML?
Yes. A text editor changes headers and body text. Edit a copy, because one wrong character in the MIME parts can break the attachments.
Is EML Safe to Open?
The text is safe, but attachments can carry malware. Open messages from known senders and scan attachments first.
How do You Save an Email as EML?
New Outlook saves messages as EML with the Save as option on the message menu. Mail programs like Thunderbird save EML with Save As.
Why does Notepad Show Lots of Code for EML?
Notepad shows the raw headers and MIME parts. Open the file in a mail program to see the formatted message.
Author's Verdict
EML is the safest format for moving single emails between programs, because most mail apps understand it.
Open them in a mail program and scan attachments first. Use a text editor only for header checks.
Key Takeaways
- EML stores one email message as plain text.
- Outlook, Thunderbird and Apple Mail open the file.
- Scan attachments before you open messages from strangers.