RFC 2045-2049: MIME (RFC 2045 through 2049): Attachments and HTML Emails
Overview article covering all five MIME RFCs as a suite: format, media types, header extensions, registration, and conformance.
MIME
RFC 6152: SMTP Service Extension for 8-bit MIME Transport
Defines the 8BITMIME SMTP extension, allowing 8-bit message content without base64 encoding.
RFC 2045: MIME Part One: Format of Internet Message Bodies
Defines the MIME content-type header and the framework for non-ASCII message bodies.
