code: func (m *MailYak) AddHeader(name, value string) {
  	m.headers[m.trimRegex.ReplaceAllString(name, "")] = mime.QEncoding.Encode("UTF-8", m.trimRegex.ReplaceAllString(value, ""))
  }
docs: // AddHeader adds an arbitrary email header.
  //
  // If value contains non-ASCII characters, it is Q-encoded according to RFC1342.
  // As always, validate any user input before adding it to a message, as this
  // method may enable an attacker to override the standard headers and, for
  // example, BCC themselves in a password reset email to a different user.