sendmail.jsp: How do I know that mail was send ?

I have a small form on my web page with which the visitors send me a
comment.

In sendmail.jsp it was written:
....
<%
    SendMail sendMail = new SendMail();
    sendMail.sendMail(to, from, subject, content, "localhost");

%>
....
to, from, subject, content
pokupim iz html forme.

sendMail method in SendMail class looks like this:

    public static void sendMail(String to, String from, String subject,
String content, String host) throws Exception {
        // create some properties and get the default Session

        host = "localhost";

        Properties props = new Properties();
        props.put("mail.smtp.host", host);

        Session session = Session.getDefaultInstance(props, null);

        try {
            // create a message
            MimeMessage msg = new MimeMessage(session);
            msg.setFrom(new InternetAddress(from));
   msg.setHeader("Content-Type", "text/plain; charset=windows-1250");
            InternetAddress[] address = {new InternetAddress(to)};
            msg.setRecipients(Message.RecipientType.TO, address);
            msg.setSubject(subject,"windows-1250");
   //msg.setHeader("Content-Transfer-Encoding", "8bit");

            msg.setSentDate(new Date());
            // If the desired charset is known, you can use
            // setText(text, charset)
            //msg.setText(content,"Cp1250");
            msg.setText(content,"windows-1250");

            Transport.send(msg);
        } catch (MessagingException mex) {
            System.out.println("\n--Exception handling in
msgsendsample.java");

            mex.printStackTrace();
            System.out.println();
            Exception ex = mex;
            do {
                if (ex instanceof SendFailedException) {
                    SendFailedException sfex = (SendFailedException)ex;
                    Address[] invalid = sfex.getInvalidAddresses();
                    if (invalid != null) {
                        System.out.println(" ** Invalid Addresses");
                        if (invalid != null) {
                            for (int i = 0; i < invalid.length; i++)
                                System.out.println(" " +
invalid[i]);
                        }
                    }
                    Address[] validUnsent = sfex.getValidUnsentAddresses();
                    if (validUnsent != null) {
                        System.out.println(" ** ValidUnsent Addresses");
                        if (validUnsent != null) {
                            for (int i = 0; i < validUnsent.length; i++)
                                System.out.println("
"+validUnsent[i]);
                        }
                    }
                    Address[] validSent = sfex.getValidSentAddresses();
                    if (validSent != null) {
                        System.out.println(" ** ValidSent Addresses");
                        if (validSent != null) {
                            for (int i = 0; i < validSent.length; i++)
                                System.out.println("
"+validSent[i]);
                        }
                    }
                }
                System.out.println();
                if (ex instanceof MessagingException)
                    ex = ((MessagingException)ex).getNextException();
                else
                    ex = null;
            } while (ex != null);
        }
    }

Code above send mail successfully if the visitor wrote "from" mail
correctly. But if the visitor leave "from field" empty or put some wrong
mail I need to send him/her a message about un/success sending of comment to
me. How to do it ?

E sad, mail posalje uspjesno ako se mail koji salje (from) navede ispravno.
Kako provjeriti da je "mail from" napisan ispravno, ili, kako provjeriti da
je mail poslan i prema tome napisati obavijest mail uspjesno poslan odnosno
nije poslan ?