EML is a plain-text file that holds a single email message

EML stands for Electronic Mail and is the standard format your email program uses to store individual messages. When you receive an email, your computer saves it as an EML file — a straightforward text document that contains the message body, the sender's address, the recipient's address, the subject line, and any attachments encoded as data inside the file.

You normally never see the EML file itself. Your email program (Outlook, Gmail, Apple Mail, Thunderbird) reads the EML file and displays it to you in a readable format. But the file exists on your computer or on the email provider's server, and you can open it with a text editor if you need to.

EML files are useful because they are portable. You can move them between different email programs, back them up to external storage, or send them to someone else. Unlike a screenshot or a PDF, an EML file preserves the actual email data — headers, timestamps, and all the technical information that proves when the message arrived and who sent it.

Key Takeaways

  • An EML file is a single email message saved as a plain-text document that any email program can read.
  • Your email program automatically creates and manages EML files in the background; you do not need to do anything to use this format.
  • You can export emails from one program and import them into another by moving the EML files, which makes switching email providers easier.
  • EML files can be opened with a text editor to see the raw email data, including headers and metadata that do not normally appear on screen.

How EML files are structured

An EML file has two main sections: the header and the body. The header contains metadata about the message — the sender's address, the recipient's address, the date it was sent, the subject line, and technical routing information. The body is the actual message text you read.

If the email has attachments, they are encoded into the EML file using a standard called MIME (Multipurpose Internet Mail Extensions). This encoding converts the attachment data into text so it can be stored in the same plain-text file. When your email program opens the EML file, it decodes the attachment and displays it separately.

You can open an EML file with any text editor — Notepad on Windows, TextEdit on Mac, or any other basic text program. When you do, you will see the raw data: the email headers at the top, then a blank line, then the message body. If there are attachments, you will see encoded text that looks like random characters. This is normal and expected.

Why EML format matters for switching email programs

If you want to move your emails from one program to another, EML format makes that possible. Most email programs can export messages as EML files and import EML files from other programs. This means you can take your email history with you if you switch from Outlook to Thunderbird, or from one email provider to another.

The process is usually straightforward: open your current email program, select the messages you want to keep, choose "Export" or "Save As", and save them as EML files. Then open your new email program, choose "Import", and point it to the folder where you saved the EML files. The new program reads the files and adds the messages to your mailbox.

This portability is one reason EML became the standard. Email is too important to be locked into one program. If a company stops supporting their email software or you straightforward prefer a different interface, you can take your messages with you.

The difference between EML and other email formats

Other formats exist for storing email, and which one your program uses depends on the program itself. Microsoft Outlook uses a format called PST (Personal Storage Table) or OST (Offline Storage Table) on Windows, and OLM (Outlook for Mac) on Mac computers. Apple Mail uses MBOX, which is a different format that stores multiple messages in a single file rather than one message per file.

Gmail and other web-based email services do not store messages as EML files on your computer at all — they keep them on their servers. But if you read your Gmail messages using a tool like Google Takeout, you can save them as EML files for backup or transfer to another program.

The advantage of EML is that it is the most widely supported format across different email programs and operating systems. If you need to move emails between programs, EML is usually the safest choice because almost every email program can read it.

How to find and manage EML files on your computer

If you use Thunderbird, Apple Mail, or another program that stores messages as individual EML files, the files are usually kept in a folder on your computer that the email program manages automatically. On Windows, Thunderbird stores them in a folder like C:\Users\[Your Name]\AppData\Roaming\Thunderbird\Profiles\[Profile Name]\Mail. On Mac, Apple Mail stores them in ~/Library/Mail/V [version number]/MailData/Mailbox.objectdb.

You do not need to open these folders or move files around manually. Your email program handles all of that. But if you want to back up your emails, you can copy these folders to an external drive or cloud storage. If you want to export specific messages, use your email program's export feature rather than navigating the folders yourself.

If you receive an EML file from someone else — perhaps as an attachment or a backup — you can open it by double-clicking it. Your default email program will read it and display the message. If you want to open it with a different program, right-click the file, choose "Open With", and select the email program you prefer.

When you might need to work with EML files directly

Most people never need to think about EML files. Your email program handles them automatically. But there are situations where you might need to work with them directly.

If you are switching email programs and the import feature is not working, you can manually move EML files from one program's folder to another. If you need to preserve an important email for legal or record-keeping purposes, exporting it as an EML file creates a permanent copy that includes all the original metadata. If you are troubleshooting an email problem, a technical support person might ask you to export a message as an EML file so they can examine the headers and see exactly how the message was routed.

You might also encounter EML files if you read your email history from a web-based service. Some services offer data export tools that save your messages as EML files so you can back them up or move them to a different program.

Frequently Asked Questions

Can I open an EML file without an email program?

Yes. You can open an EML file with any text editor — Notepad, Word, or any other program that reads plain text. You will see the raw email data, including headers and encoded attachments. It will not look as clean as it does in your email program, but all the information is there and readable.

If I export my emails as EML files, will I lose anything?

No. EML format preserves the complete email message, including the body, headers, timestamps, and sender information. Attachments are encoded into the file. The only thing you might lose is folder organization or labels, depending on how you export. Check your email program's export settings to see what options are available.

Why does my email program use EML instead of a different format?

EML is the most widely supported format across different email programs and operating systems. It is straightforward, portable, and has been the standard for decades. Programs like Thunderbird and Apple Mail use it because it makes it straightforward for users to switch programs or back up their messages without being locked into one company's format.

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

Yes, but the method depends on what program you use. Most email programs have a "Print" or "Export as PDF" option. Open the EML file in your email program, then use the print function and choose to save as PDF. This creates a readable document, though you will lose the ability to forward or reply to the message.

What happens to EML files if I delete an email?

When you delete an email from your email program, the EML file is moved to a Trash or Deleted Items folder. If you empty the trash, the file is permanently deleted from your computer. If you want to keep important emails, export them as EML files and store them in a separate folder or on an external drive before deleting them from your email program.