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It is basically an extension of the initial e-mail protocol known as SMTP and allows the users to use the protocol for sharing various kinds of data files on the Internet such as Audio, video, images and various program files along with ASCII text as deployed in the original one.
 
They are actually special formatting instructions which are indicated in the header portion of message (not SMTP) because SMTP does not care as it looks everything as the message data purely.
 
 
 

Important Features of MIME:

  • In a single message, several attachments can be sent easily and all attachments can be non-text type.
  • There is no limitation of the length of the message. And the body of message can have multiple parts.
  • It makes Text in character sets other than ASCII possible.
  • Apart from ASCII codes, other data files can also be shared through it.
  • Different kinds of layouts, font style, colors, and size can be used in the message.
  • MIME uses the special header format to illustrate the type of format that the mail body is using. The ANSCII code is not compulsory here. Hence, it will make it simple for the email-client to understand it in the correct format.
  • Even though MIME is designed to support the SMTP, the content type which is defined in the MIME has the significance in the Communication protocols apart from the e-mail.
The web servers add the MIME header at the starting point of the circulation of web data. The web clients, e.g., MS-Outlook, etc. thus use this content-type header for finalizing the suitable viewer application for their service as indicated by the header.
 
What I like most about MIME is that it designates a boundary between email text and attachments.

MIME Headers

(i) MIME-Version
The existence of this header specifies that the message is MIME formatted. The latest version used is 1.0, hence it is shown as MIME-Version: 1.0.
 
(ii) Content-Type
It specifies the message data’s type and subtype. The default header value will appear as Content-Type: text/plain. The above type and sub-type mean that the message contains simple text.
For Example, The detailing for image, audio, and video will be like image/gif, audio/mp3, and video/mp4.
 
(iii) Content-Transfer-Encoding
It specifies the type of encoding deployed in the message body. The various encoding techniques used are 7-bit, 8-bit, binary, base-64 for binary files with attachments and quoted-printable.
 
(iv) Content-Disposition
It specifies the presentation style and the filename associated with the message.
The presentation style can be of two types, first is inline in which whenever the mail is displayed, the presentation style will automatically come up, and second is the attachment type in which it is not displayed until we perform a certain action to open it.
 
The MIME is used in the HTTP protocol to distinguish between the types of web documents used. During the communication session between the web server and a browser, firstly the web server sends the MIME content type.
For ExampleContent-disposition: attachment to browser thus the browser comes to know how it should display the content.
 

Multipart- Messages and Subtypes

There are various kinds of sub-types as mentioned below:
  • Multipart/mixed:
It is deployed for sending several elements like the plain text with attachment.
  • Multipart/alternative:
It specifies the alternative method to show the content of the message in a form which can be understood by the user’s client. Generally, it is used to display the content of the message in a text or HTML format. Please remember that the content is the same and only the format is dissimilar.
  • Multipart/signed:
It is deployed to impose a digital signature with the message in the e-mail.
  • Multipart/related:
It specifies the related message information of the whole message. This is mostly used when a web page contains various images or video files within it. Thus the overall web page is sent as a single message and in the later part, the images or videos are retrieved.
  • Multipart/mixed-replace:
It is deployed for streaming of video, i.e. an online movie in collaboration with the HTTP.
 
 
 

This Article Was Written & published by Meena R,  Senior Manager - IT, at Luminis Consulting Services Pvt. Ltd, India. 

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