What is MIME type "application/sieve"?

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

The MIME type application/sieve is used for files that contain Sieve scripts, a language solely meant for filtering email. These scripts direct how an email server processes incoming messages automatically. They are written in plain text and are typically stored with the file extension SIEVE.

Sieve rules let servers:

Automatically sort emails based on sender or subject
Redirect, forward, or file messages into specific folders
Discard or flag unwanted emails
Ensure safe and restricted processing by disallowing harmful commands

The language is designed to be simple and secure. It gives email systems a reliable way to filter messages without risk. For more technical details, see RFC 5228.

Associated file extensions

.sieve

Usage Examples

HTTP Header

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


    Content-Type: application/sieve

HTML

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


    <a href="file.dat" type="application/sieve">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/sieve');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.sieve

FAQs

What is the purpose of the application/sieve MIME type?

This MIME type identifies files containing Sieve scripts, which are used for server-side email filtering as defined in RFC 5228. These scripts instruct mail servers on how to automatically sort, discard, or forward incoming emails based on specific rules.

Which software utilizes application/sieve files?

This type is primarily used by Mail Delivery Agents (MDAs) such as Dovecot, Cyrus IMAP, and Exim. Webmail interfaces like Roundcube may also utilize this MIME type when allowing users to import, export, or edit their email filtering rules.

How do I open or edit a file with the .sieve extension?

Since application/sieve files are stored as plain text, you can open and edit them with any standard text editor like Notepad, Vim, or Sublime Text. However, the code will not run locally; it must be uploaded to a compatible mail server to function.

How do I configure Apache to serve .sieve files correctly?

To ensure your web server delivers these files with the correct Content-Type header, add the following directive to your .htaccess or configuration file: AddType application/sieve .sieve. This helps client applications identify the file as a Sieve script rather than generic text.

Do web browsers execute application/sieve files?

No, web browsers do not have built-in engines to execute Sieve scripts. If a browser encounters this MIME type, it will typically handle it as a downloadable file or display it as plain text, depending on the browser's configuration.

Is the Sieve language secure?

Yes, Sieve is designed specifically to be safe for email filtering. It intentionally lacks complex programming features like loops and external function calls, which prevents infinite loops or malicious system access when the server processes incoming mail.

What is the difference between ManageSieve and application/sieve?

ManageSieve is a network protocol used to manage scripts on a remote mail server, whereas application/sieve defines the actual file format of the script. Clients use the ManageSieve protocol to upload files with the application/sieve content type to the server.

General 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.