⟩ Explain me the basic structure of a MIME multipart message when used to transfer different content type parts. Provide a simple example?
A simple example of a MIME multipart message is as follows:
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=frontier
This is a message with multiple parts in MIME format.
--frontier
Content-Type: text/plain
This is the body of the message.
--frontier
Content-Type: application/octet-stream
Content-Transfer-Encoding: base64
PGh0bWw+CiAgPGhlYWQ+CiAgPC9oZWFkPgogIDxib2R5PgogICAgPHA+VGhpcyBpcyB0aGUg
Ym9keSBvZiB0aGUgbWVzc2FnZS48L3A+CiAgPC9ib2R5Pgo8L2h0bWw+Cg==
--frontier--
Each MIME message starts with a message header. This header contains information about the message content and boundary. In this case Content-Type: multipart/mixed; boundary=frontier means that message contains multiple parts where each part is of different content type and they are separated by --frontier as their boundary.
Each part consists of its own content header (zero or more Content- header fields) and a body. Multipart content can be nested. The content-transfer-encoding of a multipart type must always be 7bit, 8bit, or binary to avoid the complications that would be posed by multiple levels of decoding. The multipart block as a whole does not have a charset; non-ASCII characters in the part headers are handled by the Encoded-Word system, and the part bodies can have charsets specified if appropriate for their content-type.
