func NewDialer(host string, port int, username, password string) *Dialer {
	return &Dialer{
		Host:         host,
		Port:         port,
		Username:     username,
		Password:     password,
		SSL:          port == 465,
		Timeout:      10 * time.Second,
		RetryFailure: true,
	}
}
func NewDialer(host string, port int, username, password string) *Dialer {
	return &Dialer{
		Host:         host,
		Port:         port,
		Username:     username,
		Password:     password,
		SSL:          port == 465,
		Timeout:      10 * time.Second,
		RetryFailure: true,
	}
}
// NewDialer returns a new SMTP Dialer. The given parameters are used to connect
// to the SMTP server.