If a reasonable person would understand the nature of the interaction, you are protected by the First Amendment.
The Sixth Circuit had a decision looking at simiilar factual circumstances just a few weeks back in Novak v. City of Parma. In that case, a man created a Facebook page that purported to belong to the Parma Police Department. Obviously, the police were butthurt and arrested him. Even though the page was obviously intended to mock the police, the police said it was criminal because some people were confused.
The Sixth Circuit told the police to GTFO:
The officers claim that his Facebook page was false and meant to mislead the public, not a parody. But they are wrong to think that we just look to a few confused people to determine if the page is protected parody.
Our nation's long-held First Amendment protection for parody does not rise and fall with whether a few people are confused. Instead, we must apply a "reasonable reader" test. Id. Speech that "could not reasonably have been interpreted as stating actual facts" is a parody, even if "patently offensive." Id. The test is not whether one person, or even ten people, or even one hundred people were confused by Novak's page. ...
Instead, the test for parody is whether a reasonable reader would have seen Novak's Facebook page and concluded that the posts stated "actual facts."
Given that your readers have signed up for these types of interactions, it would not be reasonable to believe the e-mails contain "actual facts.
