A MIME part can have: In addition to the presentation style, the content-disposition header also provides fields for specifying the name of the file, the creation date and modification date, which can be used by the reader's mail user agent to store the attachment.
Servers insert the MIME header at the beginning of any Web transmission.
Clients use this content type or media type header to select an appropriate "player" application for the type of data the header indicates.
Some of these players are built into the Web client or browser (for example, almost all browsers come with GIF and JPEG image players as well as the ability to handle HTML files); other players may need to be downloaded.
And the result is that it would be just about impossible for the Internet to ever define a 2.0 or a 1.1." Through the use of the multipart type, MIME allows mail messages to have parts arranged in a tree structure where the leaf nodes are any non-multipart content type and the non-leaf nodes are any of a variety of multipart types.
This mechanism supports: The original MIME specifications only described the structure of mail messages.
They did not address the issue of presentation styles.
The content-disposition header field was added in RFC 2183 to specify the presentation style.
According to MIME co-creator Nathaniel Borenstein, the intention was to allow MIME to change, to advance to version 2.0 and so forth, but this decision led to the opposite outcome, making it nearly impossible to create a new version of the standard.
"We did not adequately specify how to handle a future MIME version," Borenstein said.