You download an email archive or receive an attachment ending in .eml, but a normal double-click does not show the message. What is an EML file? It is usually a saved copy of one email, including message fields, body content, and MIME-packaged attachments. The EML meaning is commonly “electronic mail” or “email.” Below, you will learn how the format works, how to view it safely on current systems, and why a PDF copy should not replace the original.
EML vs. MSG vs. MBOX: email file formats compared
EML, MSG, and MBOX all store email data, but they differ in structure and scale. EML usually holds one portable Internet-style message, MSG stores a structured Outlook item, and MBOX collects a sequence of messages.
| File extension | Format type | Architecture | Primary compatibility / use case |
| .eml | Single email message | Text-structured Internet message with optional MIME parts | Portable single-message export, transfer, and raw inspection |
| .msg | Outlook item | Compound binary file with streams, storages, and MAPI properties | Preserving richer Outlook-specific data for messages and other items |
| .mbox or no fixed extension | Mailbox database | Linear sequence of messages, commonly separated by From lines | Mailbox folders, archives, and bulk transfer; variants exist |
These formats are not interchangeable containers. Converting between them can discard application-specific properties, folder context, labels, or message relationships. The filename assigned during export is also not reliable evidence of the sender, subject, or date; use parsed message fields instead.
What is an EML file?
The .eml extension identifies a de facto saved-message representation. Its underlying email message format normally follows RFC 5322, which defines a header section and a body separated by a blank line. MIME adds fields, media types, multipart bodies, non-ASCII text, and transfer encodings. There is no separate IETF specification that defines the EML file type itself as a filesystem container.
This standards-based foundation makes the EML file format broadly portable, but not universal. An EML usually represents one message rather than a whole mailbox. It may omit server-side records, mailbox permissions, read status, folder placement, labels, and client-only properties. Much of its source is readable text, yet encoded headers, HTML, character sets, and binary content still need suitable parsing.
What’s inside an EML file? Header vs. body
The header commonly contains Date:, From:, To:, Subject:, and Message-ID: fields. It may also include Received: trace fields and Authentication-Results:. Not every field is guaranteed.
After the blank line comes the body. MIME can divide it into nested parts containing plain text, HTML, inline resources, and attachments. A multipart message can offer both text and HTML versions or combine a message with files. Base64 is common for binary attachments and adds roughly one-third to the encoded payload before line wrapping, but it is not mandatory; quoted-printable and other transfer encodings also occur.
How to open an EML file on any device
Before you open EML files, consider where they came from. If a message is unexpected or suspicious, do not follow links, open attachments, enable active content, reply, or load remote images. Do not upload private, regulated, or suspicious mail to a public viewer. A raw-text working copy can reduce accidental rendering, but it does not prove that the content is safe or authentic.
Opening EML files on Windows
- In File Explorer, double-click the file if new Outlook is already associated with .eml.
- If it is not, right-click the file and select Open with > Outlook (new). You can also drag the file onto the Outlook reading pane.
- To inspect source, right-click a working copy and choose Open with > Notepad.
Notepad shows header lines, MIME boundaries, and encoded data rather than a decoded email. Windows Mail support ended in 2024, so instructions that depend on that retired app are outdated. For the search phrase “how to open EML file,” current Outlook and raw text are the practical Windows choices.
Opening EML files on Mac
In Finder, try double-clicking the file or right-click it and choose Open With > Mail when Apple Mail is available and configured. Account requirements vary, so this is not guaranteed on every Mac. To read EML file structure without a rendered message view, open a duplicate in a plain-text editor. Encoded MIME parts and attachments will remain undecoded.
Opening EML files in a web browser
A current browser may show raw MIME source when you drag a local EML into a tab, but it may instead download the file or hand it to another app. Browsers do not reliably decode message formatting or expose attachments across platforms. Never rename EML to HTML or MHT: changing the suffix does not parse MIME and may render untrusted content. For suspicious messages, do not use a browser.
How to convert EML files to PDF
Convert with native print-to-PDF
A PDF is useful as a fixed-layout reading, printing, or sharing copy. On Windows, open a trusted message in new Outlook, select More actions > Print > Print, choose Microsoft Print to PDF, and save. On macOS, open a trusted message in Apple Mail and choose File > Export as PDF. You can also use File > Print > PDF > Save as PDF.
For trusted, non-sensitive email only, you can convert EML file to PDF with our browser tool. Do not upload confidential, regulated, legal, or suspicious material to an unapproved service. Whether you print locally or convert online, keep the original EML unchanged.
PDF documents preserve a rendered page layout, not the complete message structure. Conversion may omit raw fields, MIME boundaries, independent attachments, and data needed to verify signatures. An attachment such as one of your Microsoft Word files may not remain separately reviewable in the PDF. For fixed-layout sharing, see PDF vs Word documents; if you send the result, follow sensible practices for sending PDF attachments.
What raw EML headers can and cannot tell you
Security teams inspect raw messages to gather evidence about routing and authentication. Preserve the original unchanged, record its source when provenance matters, and analyze a working copy with approved tools. Editing headers or body bytes can invalidate a DKIM signature and destroy byte-for-byte integrity.
Inspecting routing and authentication signals
Received: fields describe mail-system hops and are generally added as a message travels. Analysts assess the chain relative to a known trusted gateway; fields below that boundary may be forged. Forwarders, relays, network translation, and privacy controls can also hide an originating device, so these lines do not necessarily reveal a person’s “real IP.”
Authentication-Results: reports what a receiving service observed, but the field is not self-authenticating. SPF checks whether a host was authorized for an SMTP envelope identity. DKIM checks a domain signature over selected fields and body content. DMARC adds alignment and policy context. Passes and failures are signals, not proof of identity, spoofing, or malicious intent; forwarding and message modification can produce legitimate failures.
Uncovering hidden links and encoded attachments
A raw view may expose an HTML href, MIME media type, filename, or transfer encoding without intentionally activating it. However, a target can be encoded, redirected, assembled in markup, or disguised with a lookalike domain. Do not visit a discovered address, decode or extract a suspicious payload, or open an attachment. Send the preserved file to your organization’s security team or another qualified professional using an approved process.
Conclusion
An EML is usually a text-structured copy of one email based on Internet Message Format and MIME conventions. Use new Outlook or Apple Mail for a rendered view when the source is trusted, and a text editor on a working copy for cautious source inspection. Browser behavior is inconsistent, and extension renaming is not a solution. If you create a PDF for convenient reading or sharing, preserve the original EML because the derivative cannot retain every header, attachment relationship, or verification detail.