What Is an EML File? How to Open, View, and Convert EML Files

If you've received a file with a .eml extension and aren't sure what to do with it, you're not alone. EML files show up in a few distinct situations: an IT admin exported messages from a departing employee's inbox, a legal team delivered a set of records for review, a Google Vault or Microsoft Purview export landed in your downloads folder, or an email archiving system produced a backup. The good news is that EML is a widely supported format with several straightforward options for opening, viewing, and converting it.

What Is an EML File?

An EML file is a saved email message in a standard text-based format. The .eml extension follows the RFC 2822 standard that governs how internet email messages are structured. Because it's an open standard, virtually every email client can read EML files, which is why EML is often treated as the default interchange format when email needs to be moved between systems or preserved for the long term.

Inside an EML file you'll find everything that makes up a complete email message: the headers (From, To, CC, BCC, Subject, Date, Message-ID), the message body in plain text, HTML, or both, and any attachments encoded as MIME parts within the same file. The file is technically plain text, so you can open it in a text editor and read the raw content, though encoded attachments won't be usable that way.

EML files are sometimes compared to MSG files. The distinction is simple: EML is an open, cross-platform format compatible with almost every email client. MSG is Microsoft's proprietary format, used natively by Outlook, and stores some additional Outlook-specific data. If you received a file from a Windows-heavy enterprise environment, you may encounter both. Most approaches for opening and converting EML files apply to MSG as well, but the specific tools differ slightly.

Where EML Files Come From

Knowing the source of an EML file helps you understand what you're working with and what tools fit the job.

• Email clients. Mozilla Thunderbird, Apple Mail, the older Windows Live Mail, and Outlook Express all use EML as their native storage format. Exporting a folder of messages from any of these clients produces a directory of EML files, one per message.
• Google Vault. When you export email from Google Vault (Google's eDiscovery and archiving tool), messages can come out as MBOX archives or individual EML files depending on the export configuration. Legal teams doing discovery on Gmail frequently encounter EML packages from this source.
• Microsoft 365 Content Search and Purview. Exports from Microsoft Purview Compliance or the M365 admin center typically produce PST files, but these are often converted to individual EML files when ingested into review platforms.
• eDiscovery packages. When forensic vendors or opposing counsel produce email records for a legal matter, they often use EML because it's platform-neutral and readable without specialized software. A zip file full of .eml files from a law firm or IT team almost always came from this kind of production workflow.
• Email archiving systems. Corporate archiving solutions frequently export in EML format for portability. EML is the preferred format when the goal is long-term preservation and interoperability across different systems.

How to Open an EML File on Windows

Outlook and Windows Mail

If you have Microsoft Outlook installed, you can open an EML file by dragging it into an open Outlook window. Outlook doesn't register itself as the default handler for .eml files during installation, so double-clicking won't work on its own, but dragging the file onto an open Outlook session renders it as a readable message. Outlook 2016 and later handle this reliably. For the Windows 11 Mail app (now also branded as Outlook), right-click the file and choose "Open with" to select it from the list of programs.

Mozilla Thunderbird

Thunderbird is a free, open-source email client that handles EML files natively and works on Windows, Mac, and Linux. You can install it without setting up an email account and use it purely as a file viewer. Once installed, right-click any EML file, choose "Open with," and select Thunderbird. To make that permanent, set Thunderbird as the default handler for .eml files in Windows Settings. Thunderbird renders HTML emails accurately and handles attachments cleanly, which matters when you're reviewing formatted messages with embedded images or document attachments.

How to Open an EML File on Mac

On macOS, Apple Mail is the most direct option. Double-clicking an EML file usually opens it in Apple Mail automatically, displaying the message with full formatting, headers, and any attachments. If you have multiple email clients installed, right-click and choose "Open With" to specify which one to use.

Mozilla Thunderbird works on Mac exactly as it does on Windows: install it, set it as the default for .eml files, and double-click to open. This is useful when you need a consistent workflow across platforms, or when Apple Mail doesn't render a specific message correctly (usually a compatibility issue with certain HTML email templates).

For a lighter-weight option, there are Mac apps purpose-built for EML browsing. These are most useful when you receive EML files regularly and don't want them interfering with your normal inbox setup.

EML File Viewers and Readers

An EML file viewer is a tool designed specifically for reading EML files without requiring a configured email account. The main use case is reviewing exported email records: a folder of hundreds or thousands of EML files where you need to browse, search, and inspect messages without importing everything into an active inbox.

There are three main categories to consider:

• Online EML viewers. Browser-based tools where you upload an EML file and view it rendered in the browser. Good for a single file you need to open quickly. Not appropriate for large batches or anything sensitive, because you're uploading potentially confidential email content to a third-party service.
• Desktop EML readers. Standalone applications that let you browse a folder of EML files with a preview panel. Most support search and export. Better for larger sets of files and situations where the data needs to stay local.
• Full email clients (Thunderbird, Apple Mail, Outlook). Not designed specifically for viewing exported EML files, but capable of it and already installed on most machines. The most practical starting point.

How to Convert EML to PDF

PDF is the standard format for sharing email records in legal and business contexts. PDFs are easy to Bates-stamp, annotate, share across platforms, and store long-term without worrying about rendering differences. Converting EML to PDF is the most common next step for people who received EML files as part of a discovery or compliance package.

Print to PDF from an Email Client

The simplest method for a small number of files: open the EML in Thunderbird or Apple Mail, then use File > Print and choose "Save as PDF" on Mac, or select a PDF printer on Windows. This works well for a handful of messages. The output quality depends on how the email client renders HTML, and by default you may not get the full header information (From, To, Date, Message-ID) in the PDF unless you configure the client to show extended headers before printing.

Online EML to PDF Converters

Browser-based tools exist that accept EML uploads and return PDFs. They're quick for one or two files. The concern is data handling: uploading personnel records, confidential business communications, or anything subject to a legal hold to an unvetted third-party service is a risk that most legal and compliance teams can't accept. Read the privacy policy before using any online converter for anything sensitive, and check whether the service retains uploaded content.

Batch EML to PDF Conversion Tools

When you're working through dozens or hundreds of EML files, batch conversion tools are the practical choice. These are typically Windows desktop applications that process a folder of EML files and output a corresponding folder of PDFs. The better ones preserve metadata, handle attachments, and let you search or filter before converting. This is worth the extra setup cost when the alternative is printing hundreds of messages one at a time.

EML Files in eDiscovery

EML is a common output format in email discovery because it's platform-neutral and doesn't require Outlook or any specific software to read. A few sources produce EML files specifically:

• Google Vault exports individual messages as EML files when exported at the message level, rather than as MBOX archives.
• Microsoft Purview and M365 Content Search export PST files that third-party tools often convert to individual EML files during processing for review platforms.
• Third-party eDiscovery tools frequently use EML as an intermediate format before ingesting into review platforms like Relativity or Everlaw.

One thing that matters specifically in legal review: the raw headers inside an EML file are the authoritative record of how and when a message was sent. Email clients render a simplified view, often hiding fields like Message-ID, Received timestamps, and BCC recipients that were stripped from the delivered copy. If a dispute turns on whether a message was actually received, or the precise time it was sent, looking at the raw headers is the definitive check. Most email clients have a "View Source" or "Show Raw Message" option for this.

EML files also preserve threading information through the In-Reply-To and References headers. This allows conversation threads to be reconstructed even when messages from different custodians arrive separately, which matters when you're trying to establish the sequence of a negotiation or decision-making process.

Are EML Files Safe to Open?

An EML file is a text file. The format itself isn't dangerous. The risk is what the file contains: phishing links in the message body, malicious attachments (executables, Office documents with macros, PDFs with embedded scripts), or HTML that loads remote tracking content when rendered by an email client.

If the EML file came from a trusted source, like an IT team, a legal production, or your own export, it's safe to open. If you received an unexpected EML attachment from an unknown sender, apply the same judgment you'd apply to a suspicious email: don't click links, don't open attachments you weren't expecting, and consider inspecting the raw file in a text editor before opening it in an email client. The text editor approach lets you see what's in the file without rendering HTML or executing anything.

The Part That's Harder Than Opening the File

EML is one of the more durable formats around. It's based on a decades-old open standard, readable with nothing more than a text editor, and will be just as accessible twenty years from now as it is today. That's genuinely useful compared to proprietary formats tied to specific software versions.

But the harder problem for anyone receiving EML files professionally isn't the format, it's verifying the export is complete. Email export tools fail silently in predictable ways: attachments are omitted without any error in the parent EML file, messages at the boundaries of date ranges are missed due to timezone handling, BCC recipients disappear from headers in the delivered copies, and certain encoding edge cases cause messages to export as corrupted or blank files.

Before certifying a set of EML files as a complete record, whether for legal production or internal compliance, it's worth checking for gaps in message date sequences, inconsistencies between expected message counts and what was delivered, and any messages with references to attachments that don't appear in the file. The format makes the records readable. Checking the collection makes them trustworthy.