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Guide

How to open an MSG file without Outlook

Published September 29, 2026

A .msg file is Microsoft Outlook’s proprietary message format — a binary container (the same Compound File format used by old .doc and .xls files) rather than the plain text .eml uses. That’s why double-clicking one on a machine without Outlook usually does nothing, or opens it as raw binary junk in a text editor.

Why .msg is harder than .eml

Outlook stores the message body, headers, and attachments as separate binary “streams” inside one compound file, and — crucially — often stores the body as compressed Rich Text (RTF), not plain HTML. A tool has to understand both the container format and Outlook’s RTF compression to render the message correctly, which is why generic file viewers can’t just “read” a .msg the way they can an .eml.

Three ways to open it without Outlook installed

  1. A browser-based MSG viewer. Drop the file in; it decodes the compound-file structure and, if needed, decompresses the RTF body locally, without uploading the file anywhere.
  2. Convert it to .eml first, if you have a tool available that supports that conversion — .eml is plain text and far more widely supported by lightweight viewers and older mail clients.
  3. Open it in a webmail account you control by uploading it as an attachment to a draft in some webmail clients that offer a “preview” for .msg attachments — check first whether that upload is something you’re comfortable with for a private message.

What you might lose in conversion

Outlook-specific metadata — categories, flags, and some custom properties — often doesn’t survive being converted out of .msg. The message text, standard headers and attachments should still come through intact in a well-tested converter.

If you’re dealing with .msg files, you may also run into winmail.dat attachments, which are a different (but related) Outlook quirk. See what winmail.dat is for that one.