What is MIME type "application/ms-tnef"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

The MIME type application/ms-tnef is a format developed by Microsoft. It stands for Transport Neutral Encapsulation Format and bundles email content like rich text and file attachments.

It is used mainly in emails sent from Microsoft clients. The format ensures that complex message formatting and embedded items are preserved during transit. However, non-Microsoft applications may not interpret it correctly, which can lead to unreadable attachments.

Main Use: Packaging email message details, including rich text formatting and calendar invites.
Embedded Data: It encloses additional files into a single data stream.
Compatibility: Mostly supported by Microsoft Outlook and similar email clients.

Files using this MIME type often appear as DAT or TNEF in email attachments. For more technical details, see Wikipedia.

Associated file extensions

.dat, .tnef

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: application/ms-tnef

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="application/ms-tnef">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');
    
    http.createServer((req, res) => {
      res.setHeader('Content-Type', 'application/ms-tnef');
      res.end('Content here');
    }).listen(3000);

Associated file extensions

.dat, .tnef

FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.