.EML Email Message
.eml

Email Message

An EML file stores a single email message in the RFC 5322 Internet Message Format. It contains headers, body text or HTML, and MIME-encoded attachments as plain text. FileDex does not convert EML files but provides format reference information.

Learn more ↓
File structure
Header schema
Records structured data
Text FormatRFC 5322MIME EncodedEmail StandardOpen Format
By FileDex
Not convertible

Email messages are structured text. Format conversion between email formats is not applicable in browser.

Common questions

Can I open an EML file without an email client?

Yes. EML files are plain text. You can open them in any text editor to see headers and body content. Attachments will appear as Base64-encoded blocks.

How do I convert EML to MSG?

Use a conversion tool like Aid4Mail, Stellar Converter, or Python libraries such as extract-msg. Manual conversion requires reconstructing MAPI properties from RFC headers.

Are EML files safe to open?

The text itself is harmless, but EML files can contain phishing links in the HTML body or malicious attachments. Scan attachments with antivirus before opening them.

What makes .EML special

What is an EML file?

EML is a standard file format for email messages based on IETF RFC 5322 (Internet Message Format). Unlike Outlook's proprietary MSG format, EML is an open standard supported by virtually all email clients. EML files contain the full email including headers, body (text/HTML), and MIME-encoded attachments.

Continue reading — full technical deep dive

How to open EML files

  • Mozilla Thunderbird (Windows, macOS, Linux) — Full support
  • Microsoft Outlook (Windows, macOS) — Import support
  • Apple Mail (macOS) — Double-click to open
  • Any text editor — View raw email headers and text

Technical specifications

Property Value
Standard RFC 5322, RFC 2045-2049 (MIME)
Encoding 7-bit ASCII with MIME extensions
Body Plain text, HTML (multipart/alternative)
Attachments MIME-encoded (Base64, quoted-printable)
Headers From, To, Subject, Date, Message-ID

Common use cases

  • Email backup: Saving messages from any email client.
  • Email migration: Moving messages between platforms.
  • Forensics: Email evidence in investigations.
  • Testing: Sample emails for development and QA.

.EML compared to alternatives

..EML vs ..MSG
Openness and portability
EML is an open standard readable by any email client or text editor, while MSG requires Outlook or specialized viewers
 .EML wins
..EML vs ..MBOX
Single vs multiple message storage
MBOX stores multiple emails in a single file, while EML stores one email per file — MBOX is more efficient for bulk archival
 .MBOX wins

Technical reference

MIME Type
message/rfc822
Developer
IETF
Year Introduced
1982
Open Standard
Yes — View specification

Binary Structure

EML files are plain-text files structured as RFC 5322 messages. They begin with header fields (From, To, Subject, Date, Content-Type, etc.) followed by a blank line and the message body. Multipart messages use MIME boundary delimiters to separate text, HTML, and attachment parts. Attachments are Base64 or quoted-printable encoded inline.

1982RFC 822 defines the original Standard for ARPA Internet Text Messages1993RFC 1521 introduces MIME (Multipurpose Internet Mail Extensions) for attachments2001RFC 2822 updates the Internet Message Format with stricter syntax2008RFC 5322 supersedes RFC 2822 as the current Internet Message Format standard
Parse EML headers with Python other 
python -c "import email; msg=email.message_from_file(open('mail.eml')); print(msg['From'], msg['Subject'])"

Uses Python's built-in email module to parse and display the From and Subject headers from an EML file

Extract attachments from EML other 
munpack mail.eml

Uses the munpack utility (from mpack) to extract all MIME attachments from an EML file into the current directory

View raw EML content other 
cat mail.eml | head -50

Displays the first 50 lines of an EML file, typically showing all headers and the start of the body

EML → MSG export near-lossless Convert open-standard EML to Outlook MSG format for organizations using Microsoft Exchange
EML → PDF render lossy Render email content to PDF for archival, legal discovery, or sharing with non-email users
EML → TXT export lossy Extract plain-text body and headers for indexing or text processing
MEDIUM

Attack Vectors

  • HTML body can contain phishing links and tracking pixels
  • MIME attachments may contain malware (executables, macros)
  • Spoofed From headers can impersonate trusted senders
  • Embedded JavaScript in HTML parts (blocked by most clients)

Mitigation: FileDex does not open, execute, or parse these files. Reference page only.

Python standard library for parsing, creating, and manipulating EML/MIME messages
Free cross-platform email client with full EML support for reading, writing, and organizing
mailparser library
Node.js library for parsing EML/MIME messages into structured JavaScript objects
mpack tool
Command-line utilities for encoding and decoding MIME messages and extracting attachments