import java.io.UnsupportedEncodingException;
import java.util.Date;
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class Teste {

public static void main(String[] args) throws UnsupportedEncodingException, MessagingException {

      String host = "smtp.gmail.com";
     String user = "system.maplo@gmail.com";
     String pass = "senha";
     String to = "destinatario1@gmail.com";
     String to2 = "destinatario2@gmail.com";
     String to3 = "destinatario3@gmail.com";
     String from = "system.maplo@gmail.com";
     String subject = "Testando email";
     String messageText = "TESTE ";
     boolean sessionDebug = false;

     Properties props = System.getProperties();

     props.put("mail.smtp.starttls.enable", "true");
     props.put("mail.smtp.host", host);
     props.put("mail.smtp.port", "587");
     props.put("mail.smtp.auth", "true");
     props.put("mail.smtp.starttls.required", "true");
     props.put("mail.smtp.ssl.trust", "smtp.gmail.com");

    java.security.Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
    Session mailSession = Session.getDefaultInstance(props, null);
    mailSession.setDebug(sessionDebug);
    Message msg = new MimeMessage(mailSession);
    msg.setFrom(new InternetAddress(from, "Sistema Manplo"));
    InternetAddress[] address = {new InternetAddress(to), new InternetAddress(to2), new InternetAddress(to3)}; // aqui estão os destinatários.
    msg.setRecipients(Message.RecipientType.TO, address);
    msg.setSubject(subject);
    msg.setSentDate(new Date());
    msg.setContent(messageText, "text/html;charset=UTF-8");

    Transport transport = mailSession.getTransport("smtp");
    transport.connect(host, user, pass);
    transport.sendMessage(msg, msg.getAllRecipients());
    transport.close();

    System.out.println("Enviado com Sucesso");
    }

}