Function text_entity 

pub fn text_entity(body: &str, flowed: bool) -> String

The text/plain entity of an outgoing message: its Content-Type header and the body in canonical CRLF form. With mutt’s $text_flowed the part is declared format=flowed and the body is space-stuffed, so a reader may rewrap it (RFC 3676). The paragraphs are the editor’s doing: rmut adds no trailing spaces.