Open Outlook .msg files on any computer
When someone drags an email out of Outlook on Windows and attaches it to a message, or saves it with File → Save As, the result is an .msg file. Legal teams, IT departments and many companies use MSG to keep individual emails. The trouble starts when the person receiving it doesn't use Outlook. Macs, Chromebooks and Linux machines can't open MSG natively, and even on Windows the new Outlook app opens MSG files only with a qualifying Microsoft 365 subscription.
This MSG viewer reads the file directly in your browser. No Outlook, no Microsoft account and no upload are needed.
What's inside an MSG file
An MSG file is a small file system of its own, the Compound File Binary format, documented by Microsoft as MS-CFB, with the message stored as MAPI properties (MS-OXMSG). There are separate streams for the subject, the sender, the recipients table, the body in plain text, HTML and compressed RTF, and one storage per attachment. Attached emails are stored as complete MSG objects inside the parent.
InboxVue reads all of these. It shows:
- Sender and recipients, including display names and addresses, To/Cc/Bcc where the file contains them, and the sent and received dates.
- The body in its richest available form. HTML is shown in a sandboxed frame. When the message is stored only as compressed RTF, it's decompressed and the embedded HTML is recovered.
- Attachments with type, size and previews, plus embedded messages that open as their own emails, with a breadcrumb back to the parent.
- Meeting requests as a card with the time, location and organiser, and the transport headers if Outlook kept them.
Both modern Unicode MSG files and the older ANSI format from Outlook 2002 and earlier are supported. Outlook template files (.oft) open the same way.
Troubleshooting
"This file is protected." The message was encrypted with S/MIME or Microsoft Purview rights management. The headers are shown, but the body can only be decrypted by the intended recipient with their key, in Outlook.
There's a winmail.dat attachment inside. That happens when an MSG wraps a message that had already been converted to Outlook's TNEF format. Click it to unpack its contents; see the winmail.dat opener, or learn why winmail.dat happens.
Accented or non-Latin text looks wrong in an old MSG. ANSI files use the code page of the Windows machine that wrote them. InboxVue reads the code page from the file when it's recorded. If it isn't, choose the right one under ⋯ → Text encoding.
The file opens as an EML instead. Some systems export messages as internet email but give them a .msg extension. InboxVue detects the real format from the file contents and shows it correctly either way.
MSG viewer vs other options
| Option | Platform | Needs | Notes |
|---|---|---|---|
| InboxVue | Any browser | Nothing | No upload, embedded messages, export to PDF/EML |
| Classic Outlook for Windows | Windows | Outlook licence | Opens MSG natively |
| New Outlook for Windows / Outlook on the web | Windows, web | Qualifying Microsoft 365 subscription | Drag-drop or double-click to open |
| Outlook for Mac 16.108+ | macOS | Outlook installed | MSG support added in April 2026 |
| Desktop freeware viewers | Usually Windows | Install | Feature sets vary; check the licence for business use |
For step-by-step instructions for each route, read how to open MSG files without Outlook or, on a Mac, how to open an MSG file on Mac. If you're weighing a Windows freeware viewer, we compare one popular option in CoolUtils Mail Viewer vs InboxVue.
Next steps
If you need to send the message to someone who can't open MSG either, convert the MSG to PDF. To import it into Apple Mail, Thunderbird or Gmail, convert MSG to EML first. Already have an EML? The EML viewer handles those.