http://www.rfc-editor.org/rfc/rfc1428.txt
RFC 1428: Transition of Internet Mail from Just-Send-8 to 8bit-SMTP/MIME, G. Vaudreuil1993-02-01T23:00:00-00:00This document outlines the problems in this environment and an approach to minimizing the cost of transition from current usage of non-MIME 8bit messages to MIME. This RFC provides information for the Internet community. It does not specify an Internet standard.