EML is a plain-text file format that stores a single email message

EML stands for electronic mail, and it is simply a way of saving one email as a standalone file on your computer. When you export or download an email from Gmail, Outlook, Apple Mail, or Thunderbird, you often get an .eml file — a text document that contains the message body, all the headers (sender, recipient, subject, date), and any attachments bundled together in one package.

The format exists because email programs need a standard way to store and move messages between different systems. Instead of keeping everything locked inside a proprietary database, EML lets you save an email as a portable file you can open, share, or import into a different email program later. It is human-readable if you open it in a text editor, though the headers and encoding can look messy.

EML files are not encrypted by default and do not compress attachments — they store everything as-is. This makes them useful for archiving, but also means a single email with a large PDF or image attached can be a fairly large file.

Key Takeaways

  • EML is a standard format for saving individual email messages as files, used by most major email programs including Gmail, Outlook, and Apple Mail.
  • You can open an EML file in a text editor to read the message, headers, and attachment information, though the formatting will be raw and difficult to parse by hand.
  • EML files are portable and can be imported into different email programs, making them useful for switching email clients or backing up important messages.
  • Attachments are stored inside the EML file itself, so a message with large files attached will create a large .eml file with no compression.

When you actually encounter EML files

You will most often see .eml files when you export or download emails from your email program. Gmail lets you download individual messages as EML through the download button in the message view. Outlook can export messages as .eml when you drag them to a folder on your desktop. Thunderbird saves messages as .eml by default when you right-click and select "Save As".

You might also receive an .eml file as an attachment if someone is forwarding you an email in its raw form rather than as a screenshot or forwarded message. This is less common but happens when someone wants to preserve the exact headers and metadata of an original message — useful if you are investigating a phishing email or need proof of when something was actually sent.

How to open and read an EML file

The simplest way is to double-click the .eml file. Your computer will usually open it in your default email program, and it will display like a normal message. If that does not work, you can drag the file into your email program's window or use the import function.

If you want to see the raw content — the actual headers, encoding, and structure — open the file in a text editor like Notepad (Windows), TextEdit (Mac), or any code editor. You will see lines like "From:", "To:", "Date:", "Subject:", followed by the message body and then a long encoded section for any attachments. This raw view is rarely necessary unless you are troubleshooting delivery problems or checking whether an email is genuine.

Some email programs like Apple Mail do not use .eml as their native format but can still open them. If you are using a program that does not recognize .eml files, you can usually import them through a menu option like "Import Messages" or "Open File".

EML versus other email file formats

EML is not the only way to store emails. Outlook uses .pst (personal storage) and .ost (offline storage) files, which bundle many messages into a single database file rather than one file per message. Apple Mail uses .mbox format, which is similar to EML but stores multiple messages in one file. Thunderbird can use both .eml and .mbox depending on how you configure it.

The main difference is convenience: EML gives you one file per message, which is easy to organize and move around, but creates many small files if you have thousands of emails. PST and MBOX bundle everything together, which is more compact but harder to extract a single message from without the right program.

If you are switching email programs, EML is often the safest middle ground because almost every email client can import .eml files. If you are archiving a large folder, you might want to ask your current program to export as MBOX or PST first, since that will be faster than exporting thousands of individual .eml files.

Why EML exists and how it works technically

EML is based on a standard called RFC 5322, which defines how email messages should be formatted as plain text. This standard was created so that different email systems — whether they run on Windows, Mac, Linux, or a web server — could all understand and exchange messages in the same way. EML simply takes that standard format and saves it as a file.

The file contains three main sections: headers (metadata about the message), a blank line, and the body (the actual content). If there are attachments, they are encoded in base64, a method that converts binary data into text characters so it can be stored in a plain-text file. This is why an EML file with a photo attached looks like gibberish at the end when you open it in a text editor.

Because EML follows an open standard rather than a proprietary format, it is one of the most portable ways to store an email. You can move an .eml file between computers, email programs, and operating systems, and it will still be readable.

Security and privacy considerations with EML files

EML files are not encrypted by default. If you save an email as .eml and store it on your computer, anyone with access to your computer can open and read it. This matters if the email contains passwords, financial information, or other sensitive data. If you need to keep an EML file secure, encrypt the file itself using your operating system's built-in encryption (BitLocker on Windows, FileVault on Mac) or a tool like 7-Zip with a password.

When you receive an EML file from someone else, treat it the same way you would treat a forwarded email: check the sender address and be cautious of links or attachments. An EML file can contain malicious content just like any other email. If someone sends you an .eml file claiming to be from your bank or a service you use, verify it directly with that organization before clicking anything in the file.

If you are exporting emails to back them up, remember that the backup is only as secure as the storage location. An external hard drive in your desk drawer is less secure than an encrypted cloud backup, but more private than storing files on a shared network drive.

Frequently Asked Questions

Can I convert an EML file to PDF or another format?

Yes. Most email programs can open an .eml file and then let you print it to PDF. You can also use online converters, though be cautious about uploading sensitive emails to a third-party website. Some programs like Thunderbird have built-in export options that let you save to different formats.

What happens if I delete an EML file?

It is gone unless you have a backup. EML files are just regular files on your computer, so deleting one removes the email permanently. If you export important emails as .eml, keep them in a folder you back up regularly, either to an external drive or a cloud service.

Can I edit an EML file and send it again?

Technically yes, but not recommended. You can open an .eml file in a text editor and change the message body, but editing the headers (From, To, Date) to make an email look like it came from someone else is possible and is used in phishing scams. If you need to modify an email, import it into your email program, edit it there, and send it as a new message instead.

Why is my email program saving files as .eml instead of keeping them in the inbox?

You probably used an export or download function. Email programs normally keep messages in their own database. If you want to keep emails in your program, do not export them — just leave them in your inbox or move them to a folder. Export to .eml only when you want a backup or need to move messages to a different program.