Autoresponders should rarely if never be triggered by an incoming email in my opinion - only form submissions. While automation is a goal for some tasks and is being made more and more possible by the Internet, communication should be personal, not automated. Take pains never to anoy people with your Internet marketing, whether through automation, insincerity, rudness, or as we discuss below, misleading tactics. Another thing that annoys the heck out of the average person is being mislead. What most people want is good, solid, honest, information about what they have expressed an interest in and no more.
People become annoyed when they are mislead.
If they request one type of information and get another type of information, they feel used. This factor comes into play, among other places, in choosing a subject header for email that you do choose to send. I have read so-called marketing advice that recommends using subject headings that will get people to read your email regardless of whether the subject has anything to do with your offer. Do not do it. Another guaranteed way to annoy someone, spuring them to report you for spam, is to mislead them about the type of information they are requesting.