Glossary
What Is a .MSG File?
A .msg file is a single email message saved in Microsoft Outlook's proprietary format. Outlook creates one when you drag a message out to a folder or use File → Save As. Inside, it isn't text at all: it's an OLE compound document — the same container technology as old Office files — holding the message as a tree of MAPI properties.
Why nothing else opens .msg
Because a .msg stores Outlook's internal representation of a message rather than the internet-standard one, other mail software can't read it: double-clicking one on a Mac gets you nowhere, Gmail won't preview it, Thunderbird shrugs. The portable equivalent is .eml — the open RFC 822 format that essentially every mail client understands.
How to open a .msg file without Outlook
Our free MSG viewer decodes the file right in your browser — rendered message, plain text, and attachments — without uploading it anywhere. To leave the format behind for good, the MSG to EML converter rebuilds each message as a standards-compliant .eml, one file at a time or a whole folder in a batch.
.msg vs .eml vs PST
| .msg | .eml | PST | |
|---|---|---|---|
| Holds | One message | One message | A whole mailbox |
| Format | Proprietary (binary MAPI) | Open standard (RFC 822) | Proprietary container |
| Opens in | Outlook | Any mail client | Outlook |
If you're saving messages one at a time because you're trying to archive old Outlook mail, there are better routes — see how to back up Outlook emails.
FAQ
How do I open a .msg file on a Mac or without Outlook?
Use a browser-based viewer or a converter. InboxBucket's free MSG viewer parses the file locally in your browser — nothing is uploaded — and shows the message, its headers, and its attachments. Apple Mail cannot open .msg files directly.
How do I convert .msg to .eml?
Drop the files into the free MSG to EML converter: each message is rebuilt as a standard RFC 822 .eml with addresses, subject, date, body, and attachments preserved, and a batch downloads as a single .zip. The conversion runs locally in your browser.
Are attachments stored inside a .msg file?
Yes. Attachments are embedded in the container alongside the message, so the one file carries everything. A viewer or converter extracts them — nothing was stripped when the message was saved.
What's the difference between .msg and .eml?
Both hold one email, but .msg is Outlook's proprietary binary format while .eml is the open internet standard. A .eml opens in essentially any mail client, today or decades from now — which is what you want from an archival format.