Authority users often play important roles in a social sys- Tem. They are expected to write good reviews at product review sites; provide high quality answers in question answering systems; and share interesting content in social net- works. In the context of marketing and advertising, know- ing how users react to emails and messages from authority senders is important, given the prevalence of email in our everyday life. Using a real-life academic event, we designed and conducted an online controlled experiment to determine how email senders of different types of authority (department head, event organizer and a general email account) affect the range of response behavior of recipients, which includes opening the email, browsing the event website, and registering for the event. In addition, we proposed a systematic approach to analyze the user response behavior to email campaigns from the time the user receives the email till he/she browses the website in a seamless manner.