The format of email has been defined in a number of RFC (Request For Comments) memorandums. This evolution has occurs over four decades: beginning in the early 1970s, the format has been refined and expanded up until the present day. If you wish to further explore the expansion of the email format, then you should read the following RFC memorandum's; the earliest is listed first.
These RFC memorandums basically have dictated the format of Email. They have laid down that an email message is to be split into two parts: a header and a body. The header includes all the vital delivery information: like who sent the message; the mail server which handled the message; and the character encoding. The body of the email includes the textual and binary content of the email message.
While the above RFC (Request For Comments) memorandums deal with the "nuts and bolts" of an email message, there are also some RFC (Request For Comments) memorandums which deal with MIME (Multipurpose Internet Mail Extensions). MIME is an addition to the standard email format, and has enabled support for attachments and extra character sets. The RFC (Request For Comments) memorandums which have outlined MIME are as follows.