Visible at the top of an email, it tells the recipient where the email has come from. Most headers will show the To and From lines, which identify the sender and recipient, and the subject line, which is meant to state the email’s purpose. Recipients often make the decision to open, trash or flag the message as spam depending on these attributes. An appealing header that accurately prepares the recipient for what the email contains is the surest way to gain a user’s trust.