An EML file stores a single email message in plain text format

An EML file is a text document that contains one complete email — the message itself, the sender's address, the recipient's address, the subject line, and any attachments encoded inside. The letters stand for "electronic mail". When you export an email from Outlook, Gmail, Thunderbird, or most other email programs, you get an EML file.

The file itself is readable as plain text, which means you can open it in Notepad or any text editor and see the raw email data. This makes EML files useful for backing up important messages, moving emails between different email programs, or keeping a record of something you need to preserve exactly as it was sent.

EML files are different from the email itself living in your inbox. When you delete an email from Gmail or Outlook, it goes to trash and eventually disappears. An EML file is a standalone copy that stays on your computer or storage device until you delete it.

Key Takeaways

  • An EML file is a single exported email saved as a text document that any email program can read.
  • You create an EML file by exporting or saving an email from your email program, not by downloading something separate.
  • Opening an EML file usually means double-clicking it, which will open it in your default email program, or right-clicking to choose a different program.
  • EML files are useful for backing up important emails, moving messages between email accounts, or keeping records of communications.
  • If an EML file won't open, the file may be corrupted, or your computer may not have an email program set as the default for that file type.

How EML files are created

You do not read EML files from the internet in normal use. Instead, you create them yourself by exporting emails from your email program. In Outlook, you right-click an email and select "Save As", then choose a location on your computer. In Gmail, you use a third-party tool or export feature to read emails. In Thunderbird, you can drag an email to your desktop or a folder.

Each EML file represents exactly one email. If you export ten emails, you get ten separate EML files. This is different from other backup formats — some email programs can export entire folders as a single file, but EML is always one message per file.

The filename usually matches the email subject or sender name, though you can rename it to anything you want. The .eml extension at the end tells your computer that it is an email file.

Opening an EML file on Windows or Mac

The simplest way to open an EML file is to double-click it. Your computer will look for an email program set as the default for EML files and open the message there. If you have Outlook, Thunderbird, or Apple Mail installed, one of these is usually set as the default.

If double-clicking does not work, right-click the EML file and select "Open with" (on Windows) or "Open with" (on Mac). A list of programs will appear. Choose Outlook, Thunderbird, Apple Mail, or another email program you have installed. You can also check a box that says "Always use this program" so future EML files open the same way automatically.

If no email program appears in the list, you may need to install one first. Thunderbird is free and works on Windows and Mac. Once installed, you can set it as the default program for EML files in your system settings.

Why you might receive or create an EML file

The most common reason to work with EML files is backing up important emails. If you receive a contract, receipt, or confirmation you need to keep, exporting it as an EML file creates a permanent copy that stays on your computer even if you delete the email from your inbox or close your email account.

EML files are also used when moving emails between email programs. If you switch from Outlook to Thunderbird, or from one Gmail account to another, you can export your old emails as EML files and import them into the new program. This preserves the original send date, sender information, and any attachments.

Sometimes someone will send you an EML file as an attachment if they want to share an email conversation with you. Opening it shows you exactly what they received, with all the original formatting and headers intact.

What happens if an EML file won't open

If you double-click an EML file and nothing happens, the most likely cause is that no email program is set as the default for that file type. Go to your system settings (Settings on Windows, System Preferences on Mac) and look for "Default apps" or "File associations". Find EML in the list and set it to an email program you have installed.

If the file opens but shows garbled text or an error message, the EML file may be corrupted. This can happen if the file was damaged during read or transfer. Try opening it in a text editor like Notepad to see the raw content. If it looks like random characters, the file is likely corrupted and cannot be repaired.

If you are trying to open an EML file on a computer with no email program installed, you have two options: install a free email program like Thunderbird, or open the file in Notepad to read the message as plain text. Reading it in Notepad will show you the email content, though the formatting will be less polished than opening it in an email program.

EML files versus other email formats

EML is the most common format for individual emails, but other formats exist. PST files (used by Outlook) store entire folders of emails in one file. MBOX files (used by Thunderbird and others) can hold many emails in a single document. MSG files (also Outlook) store one email but in a different format than EML.

The main advantage of EML is that it is a plain text format, which means it is readable in any text editor and less likely to become unreadable over time. A PST file from 2005 may not open in a newer version of Outlook, but an EML file from 2005 will still open in any email program today.

If you are choosing a format to back up emails long-term, EML is a safe choice because it is straightforward and widely supported. If you need to back up an entire mailbox with folder structure, PST or MBOX may be more practical.

Frequently Asked Questions

Can I open an EML file in Gmail or Outlook online?

Not directly. Gmail and Outlook online do not have a built-in option to open EML files. You need to use the desktop version of Outlook or another email program installed on your computer. Some third-party tools can convert EML files to other formats, but the simplest approach is to use desktop software.

Is it safe to open an EML file from someone I do not know?

EML files are text documents, so they cannot contain viruses or malware on their own. However, they can contain links or attachments that are unsafe. Treat an EML file the same way you would treat an email — do not click links or read attachments unless you trust the source.

Can I edit an EML file and save the changes?

You can open an EML file in a text editor and change the text, but email programs will not recognize the edited version as a valid email. If you need to modify an email before sharing it, open it in your email program, forward it with changes, and export the new version as an EML file instead.

What do I do with an EML file after I back it up?

Store it in a folder on your computer or external drive labeled with the year or topic. Many people create a "Email Backups" folder and organize files by year or sender. If you need to retrieve the email later, straightforward double-click the file to open it in your email program.

Why is my EML file so large?

EML files that contain attachments are larger because the attachments are encoded inside the text file. A single email with a photo or PDF can be several megabytes. If file size is a concern, you can open the EML file, remove the attachment, and save it separately.