Analysis of Non-MIME Content

Internet message content that lacks a MIME-Version header can still be supported by MIME readers. The absence of a MIME-Version header makes the payload of SMTP or elsewhere non-MIME, with different behavior for inline attachments; headers such as Content-Type, Content-Disposition, and such have no special meaning. MIME readers can, nevertheless, assume the presence of a MIME-Version header and treat headers such as Content-Type, as specified in [RFC2045] and elsewhere in this document. An example of such a message is provided in section 3.1.5.

MIME writers SHOULD NOT generate messages in this format; MIME SHOULD be generated instead. MIME readers SHOULD analyze messages in this format into headers, plain text body, and attached files (possibly including a TNEF attachment).