Did he have an expectation of privacy?

A man met a woman at a small gathering of people who are all members of an organization. They did not converse directly, but were both part of the same group conversation. The next day he got her email address from the organization’s records and sent her a sexually suggestive email. She then posted it on the (closed) group Face Book page, did NOT identify him, and expressed disgust at this missive. A number of the male responders said that she shouldn’t have posted it as he had “an expectation of privacy”.
Do you agree that he did? Why or why not?