func (m *Message) SetHeader(field, value string) {
	m.Headers[field] = value
}
func (m *Message) SetHeader(field, value string) {
	m.Headers[field] = value
}
func ( m * Message ) SetHeader ( field , value string ) { m . Headers [ field ] = value }
// SetHeader sets the heder field and value for the message
SetHeader sets the heder field and value for the message