MIME | Multi-Purpose Internet Mail Extensions

Multi-Purpose Internet Mail Extensions

MIME is an extension of the original Email protocol SMTP. SMTP is a protocol used to send and receive Emails. But there are some limitations with SMTP protocol like:

• SMTP can only send ASCII test (plain text characters)
• ASCII stands for American Standard Code for Information Interchange
• SMTP can’t transmit video/audio/graphic/executable files
• SMTP servers may reject messages bigger than certain size
• SMTP can’t transmit various national language characters other than English

MIME is intended to solve these problems. MIME was defined in 1992 by the Internet Engineering Task Force (IETF).

Original email messages consisted of only ASCII text. ASCII text means that the characters available on the keyboard. In order to send files like: audio, video, graphics, pictures and zip file, one has to convert them to plain text first and then send the result of the conversion in the body of an email message. The recipient has to convert it to the binary file format again. This is very, very difficult process.

MIME standard helps extend the limited capabilities of email by allowing insertion of images, sounds, video and animations in a message. The features offered by MIME to email services are as follows:

• Support for multiple attachments in a single message
• Support for non-ASCII characters
• Support for layouts, fonts and colors which are categorized as rich text (FORMATTING)
• Support for attachments which may contain executables, audio, images and video files, etc.
• Support for unlimited message length

MIME File Types

MIME type is an email content type system (types of files that are allowed). MIME is extensible because it defines a method to register new content types. Note that MIME is a specification for formatting non-ASCII messages so that they can be sent over the Internet. Many Email clients (IE, Mozilla, Outlook etc.) now support MIME, which enables them to send and receive graphics, audio, and video files via Internet.

In addition to e-mail applications, Web browsers also support various MIME types. This enables the browser to display files that are not in HTML format.

There are many, many different MIME types. On the web the most common ones are used with multimedia such as audio files and video files. It is also possible to define your own MIME types. Here are some examples of common mime file types seen on the web: