smtp

var Send = func(localName, serverAddress string, enableStartTLS, enableImplicitTLS bool, a gosmtp.Auth, from string, to []string, msg []byte) error {
	host, _, _ := net.SplitHostPort(serverAddress)

	var c *gosmtp.Client
	var err error

	if enableImplicitTLS {
		// Implicit TLS (SMTPS): wrap connection in TLS before any SMTP command.
		// Typically used on port 465.
		var conn *tls.Conn
		conn, err = tls.Dial("tcp", serverAddress, &tls.Config{ServerName: host})
		if err != nil {
			return err
		}
		c, err = gosmtp.NewClient(conn, host)
		if err != nil {
			return err
		}
	} else {
		c, err = gosmtp.Dial(serverAddress)
		if err != nil {
			return err
		}
	}
	defer func() { _ = c.Close() }()
	if err = c.Hello(localName); err != nil {
		return err
	}
	if enableStartTLS && !enableImplicitTLS {
		if ok, _ := c.Extension("STARTTLS"); ok {
			config := &tls.Config{ServerName: host}
			if err = c.StartTLS(config); err != nil {
				return err
			}
		}
	}
	if a != nil {
		if ok, _ := c.Extension("AUTH"); !ok {
			return errors.New("smtp: server doesn't support AUTH")
		}
		if err = c.Auth(a); err != nil {
			return err
		}
	}
	if err = c.Mail(from); err != nil {
		return err
	}
	for _, addr := range to {
		if err = c.Rcpt(addr); err != nil {
			return err
		}
	}
	w, err := c.Data()
	if err != nil {
		return err
	}
	_, err = w.Write(msg)
	if err != nil {
		return err
	}
	err = w.Close()
	if err != nil {
		return err
	}
	return c.Quit()
}