# .msg MIME Type: application/vnd.ms-outlook

> Outlook's binary message format. Not registered with IANA, but the type everyone uses for .msg files.

- MIME type: `application/vnd.ms-outlook`
- Extensions: .msg
- Content-Type header: `application/vnd.ms-outlook`
- Compress in transit: no (already compressed)
- File signature: `D0 CF 11 E0 A1 B1 1A E1` (the OLE2 compound-file signature shared by legacy Office formats)

## Good to know

- Only Outlook opens `.msg` files natively. Convert them to `.eml` for other mail clients or for archiving.
- Browsers may report `.msg` uploads as `application/octet-stream`; check for the OLE2 signature instead of trusting the type.

## Server configuration

### nginx (inside the types block in mime.types)

```
application/vnd.ms-outlook msg;
```

### Apache (.htaccess or server config)

```
AddType application/vnd.ms-outlook .msg
```

### Express

```
res.set("Content-Type", "application/vnd.ms-outlook");
```

### Python

```
import mimetypes

mimetypes.add_type("application/vnd.ms-outlook", ".msg")
```

### HTML file input

```
<input type="file" accept=".msg,application/vnd.ms-outlook">
```

## FAQ

### What is the MIME type for .msg files?

`application/vnd.ms-outlook`.

### What Content-Type header should a .msg file be served with?

`Content-Type: application/vnd.ms-outlook`. It's already compressed, so servers shouldn't gzip it.

### How can I tell if a file is really a .msg?

Check its bytes rather than the extension: MSG files start with `D0 CF 11 E0 A1 B1 1A E1` — the OLE2 compound-file signature shared by legacy Office formats. On the command line, `file --mime-type name.msg` does this for you.

## Related types

- [.eml — message/rfc822](https://www.devkult.com/mime/eml.md)
- [.doc — application/msword](https://www.devkult.com/mime/doc.md)

Open the interactive page: https://www.devkult.com/mime/msg