RFC1341 states that: In general, user agents that compose multipart/alternative entities should place the body parts in increasing order of preference, that is, with the preferred format last.
RFC1341指出：一般來說，組成多部分/替代實體的用戶代理應該按照優先級遞增的順序放置正文部分，也就是說，首選格式是最後一個。