Erro ao enviar email pelo Java

public void enviarEmail(List destinatarios, String assunto, String mensagem, String remetente) throws MessagingException, IOException {
        props.clear();
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.auth", "true");

        Session session = Session.getInstance(props, ma);
        session.setDebug(false);

        Message msg = new MimeMessage(session);

        InternetAddress addressFrom = new InternetAddress(remetente);
        msg.setFrom(addressFrom);

        InternetAddress[] addressTo = new InternetAddress[destinatarios.size()];
        for (int i = 0; i < destinatarios.size(); i++) {
            addressTo[i] = new InternetAddress(destinatarios.get(i).toString());
        }

        msg.setRecipients(Message.RecipientType.TO, addressTo);

        msg.setSubject(assunto);
        msg.setContent(mensagem, "text/plain");

        Transport.send(msg);
    }

class MyAuthenticator extends Authenticator {
        String remetente;
        String senha;
        MyAuthenticator(String remetente, String senha) {
            super();
            this.remetente = remetente;
            this.senha = senha;
        }

        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(remetente, senha);
        }
    }

public class Email {

    private String destinatario;
    private String senhaDestinatario;
    private String para;
    private String assunto;
    private String menssagem;

    public Email(String destinatario, String senhaDestinatario, String para, String assunto, String menssagem) {
        this.destinatario = destinatario;
        this.senhaDestinatario = senhaDestinatario;
        this.para = para;
        this.assunto = assunto;
        this.menssagem = menssagem;
    }


    public String getAssunto() {
        return assunto;
    }

    public void setAssunto(String assunto) {
        this.assunto = assunto;
    }

    public String getDestinatario() {
        return destinatario;
    }

    public void setDestinatario(String destinatario) {
        this.destinatario = destinatario;
    }

    public String getMenssagem() {
        return menssagem;
    }

    public void setMenssagem(String menssagem) {
        this.menssagem = menssagem;
    }

    public String getPara() {
        return para;
    }

    public void setPara(String para) {
        this.para = para;
    }

    public void setSenhaDestinatario(String senhaDestinatario) {
        this.senhaDestinatario = senhaDestinatario;
    }



    public void enviarMail() throws MessagingException, Exception {
        try {
            Properties props = new Properties();
            props.put("mail.smtp.host", "smtp.gmail.com");
            props.put("mail.smtp.starttls.enable", "true");
            props.put("mail.smtp.port", "587");
            props.put("mail.smtp.auth", "true");
            Autenticador autenticador = new Autenticador(destinatario, senhaDestinatario);

            Session session = Session.getInstance(props, autenticador);
            MimeMessage msg = new MimeMessage(session);
            // "de" e "para"!!
            msg.setFrom(new InternetAddress(destinatario));
            msg.setRecipient(Message.RecipientType.TO, new InternetAddress(para));
            // nao esqueca da data!
            // ou ira 31/12/1969 !!!
            msg.setSentDate(new Date());
            msg.setSubject(assunto);
            msg.setText(menssagem);
            // enviando mensagem (tentando)
            Transport.send(msg);
        } catch (AddressException e) {
            e.printStackTrace();
            throw e;
            // nunca deixe catches vazios!
        } catch (MessagingException e) {
            e.printStackTrace();
            throw e;// nunca deixe catches vazios!
        }
    }

    class Autenticador extends Authenticator {

        String remetente;
        String senha;

        Autenticador (String remetente, String senha) {
            super();
            this.remetente = remetente;
            this.senha = senha;
        }

        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(remetente, senha);
        }
    }

SEVERE: javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 587;
  nested exception is:
        java.net.ConnectException: Connection refused: connect
        at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1706)
        at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:525)
        at javax.mail.Service.connect(Service.java:313)
        at javax.mail.Service.connect(Service.java:172)
        at javax.mail.Service.connect(Service.java:121)
        at javax.mail.Transport.send0(Transport.java:190)
        at javax.mail.Transport.send(Transport.java:120)
        at Utilitarios.Email.enviarMail(Email.java:98)
        at apresentacao.AcessoMB.resetarSenha(AcessoMB.java:91)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at com.sun.el.parser.AstValue.invoke(AstValue.java:234)
        at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297)
        at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98)
        at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
        at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
        at javax.faces.component.UICommand.broadcast(UICommand.java:315)
        at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775)
        at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267)
        at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
        at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
        at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
        at javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)
        at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97)
        at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185)
        at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165)
        at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
        at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
        at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
        at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
        at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
        at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
        at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
        at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
        at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.net.ConnectException: Connection refused: connect
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
        at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
        at java.net.Socket.connect(Socket.java:525)
        at java.net.Socket.connect(Socket.java:475)
        at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:284)
        at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:227)
        at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1672)
        ... 48 more