Yes, it should have. If a multipart/alternate mail only has a text/html part, it should be a text/html mail.
No. The standard allows multipart/alternative to contain only one part. See the comment in RFC 2046 5.1.1 : NOTE: Experience has shown that a "multipart" media type with a single body part is useful for sending non-text media types. At any rate, our job here is to detect spam, not be the RFC police. There is legitimate software that creates multipart/alternative messages with only one part that is html. Joseph Brennan Columbia University Information Technology
