What is a .eml file?
Email Message · Data · Internet Engineering Task Force · 1982
EML stores a single email message as a plain-text file, headers and body together, in essentially the same format mail servers use to pass messages around. Dragging a message out of Thunderbird, Apple Mail or many webmail clients onto your desktop creates one.
What is a .eml file used for?
An EML file is a single saved email: the message headers (From, To, Subject, Date and the rest) followed by the body, in the same plain-text format email servers actually exchange internally.
Attachments travel inside the same file, encoded as MIME parts, so an EML with photos attached is larger than the visible text alone; that encoding is what lets a plain-text file carry images and other binaries.
Thunderbird, Apple Mail and most webmail 'save message' or 'download' features produce an EML, which is why dragging an email out of one of those apps onto your desktop usually creates a .eml file.
The header-and-body structure follows RFC 5322 (the modern successor to RFC 822), the same specification that defines how mail servers format a message in the first place.
How to open a .eml file
The .eml format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- Outlook
- Thunderbird
- any text editor (headers)
macOS
- Thunderbird
Linux
- Thunderbird
- any text editor
Web
- Some webmail 'import' features
How to convert a .eml file
You can convert a .eml file to PDF using a conversion tool or the export menu of an app that opens it.
.eml file signature (magic bytes)
Programs recognise a .eml file by the bytes at the start of the file, not by its name. These are the signatures for EML.
| Hex signature | Offset | Note |
|---|---|---|
| (no fixed signature) | 0 | no fixed signature; plain-text RFC 5322 headers, typically starting with a field like 'From:' or 'Return-Path:' |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .eml file?
EML stores a single email message as a plain-text file, headers and body together, in essentially the same format mail servers use to pass messages around. Dragging a message out of Thunderbird, Apple Mail or many webmail clients onto your desktop creates one.
How do I open an EML file?
Double-click it and it opens in your default mail app, such as Outlook, Thunderbird or Apple Mail. Since it is plain text underneath, a text editor also shows the raw headers and body.
What is the difference between EML and MSG?
Both save a single email to a file. EML is the plain-text format used across most mail clients (Thunderbird, Apple Mail, and Gmail exports), while MSG is Outlook's own binary format. Outlook can usually open an EML, and most mail apps can convert an MSG dragged in from Outlook.
Related formats
Sources
Details on this page were checked against authoritative references: