public String sendMail(String to, String sub, String msg) {
String res = null;
try {
    final String username = "admin@gmail.com"; //mailConfigMast.getUsername();
    final String password = "password";
    final String mailHost = "smtp.gmail.com";
    final String mailPort = "587";
    final String mailFrom = "admin@gmail.com"; // mailConfigMast.getFrom_mail();
    final String mailFromName = "admin@gmail.com"; //mailConfigMast.getFromname();

    Properties props = new Properties();
    props.put("mail.smtp.starttls.enable", "true"); // added this line
    props.put("mail.smtp.host", mailHost);
    props.put("mail.smtp.port", mailPort);
    props.put("mail.smtp.auth", "true");
    props.put("mail.smtp.starttls.required", "true"); // added this line
    props.put("mail.smtp.user", username);
    props.put("mail.smtp.ssl.trust", "smtp.gmail.com");
    props.put("mail.debug", "true");

    Session session = Session.getInstance(props, new javax.mail.Authenticator() {
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(username, password);
        }
    });

    Message message = new MimeMessage(session);
    message.setFrom(new InternetAddress(mailFrom, mailFromName));
    message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
    message.setSubject(sub);

    BodyPart messageBodyPart = new MimeBodyPart();
    messageBodyPart.setContent(msg, "text/html");
    Multipart multipart = new MimeMultipart();
    multipart.addBodyPart(messageBodyPart);
    messageBodyPart = new MimeBodyPart();

    message.setContent(multipart);
    message.saveChanges();
    Transport.send(message);

    System.out.println("Sent message successfully....to " + to);
    res = " Mail send OK";

} catch (MessagingException me) {
    me.printStackTrace();
    System.out.println("problem in sendmail****************** " + me.toString());
} catch (Exception e) {
    e.printStackTrace();
    System.out.println("problem in sendmail****************** " + e.toString());
}

return res;

DEBUG: JavaMail version 1.4ea
DEBUG: java.io.FileNotFoundException: /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.111-1.b15.el7_2.x86_64/jre/lib/javamail.providers (No such file or directory)
DEBUG: !anyLoaded
DEBUG: not loading resource: /META-INF/javamail.providers
DEBUG: successfully loaded resource: /META-INF/javamail.default.providers
DEBUG: Tables of loaded providers
DEBUG: Providers Listed By Class Name: {com.sun.mail.smtp.SMTPSSLTransport=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Sun Microsystems, Inc], com.sun.mail.smtp.SMTPTransport=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun Microsystems, Inc], com.sun.mail.imap.IMAPSSLStore=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Sun Microsystems, Inc], com.sun.mail.pop3.POP3SSLStore=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Sun Microsystems, Inc], com.sun.mail.imap.IMAPStore=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Sun Microsystems, Inc], com.sun.mail.pop3.POP3Store=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Sun Microsystems, Inc]}
DEBUG: Providers Listed By Protocol: {imaps=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Sun Microsystems, Inc], imap=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Sun Microsystems, Inc], smtps=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Sun Microsystems, Inc], pop3=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Sun Microsystems, Inc], pop3s=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Sun Microsystems, Inc], smtp=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun Microsystems, Inc]}
DEBUG: successfully loaded resource: /META-INF/javamail.default.address.map
DEBUG: !anyLoaded
DEBUG: not loading resource: /META-INF/javamail.address.map
DEBUG: java.io.FileNotFoundException: /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.111-1.b15.el7_2.x86_64/jre/lib/javamail.address.map (No such file or directory)
DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun Microsystems, Inc]
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: trying to connect to host "smtp.gmail.com", port 587, isSSL false
220 smtp.gmail.com ESMTP 21sm19763693pfy.4 - gsmtp
DEBUG SMTP: connected to host "smtp.gmail.com", port: 587

EHLO TestWalletApp
250-smtp.gmail.com at your service, [125.99.51.226]
250-SIZE 35882577
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-PIPELINING
250 SMTPUTF8
DEBUG SMTP: Found extension "SIZE", arg "35882577"
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "STARTTLS", arg ""
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "SMTPUTF8", arg ""
STARTTLS
220 2.0.0 Ready to start TLS
EHLO TestWalletApp
javax.mail.MessagingException: Can't send command to SMTP host;
  nested exception is:
        javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1420)
        at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1408)
        at com.sun.mail.smtp.SMTPTransport.ehlo(SMTPTransport.java:847)
        at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:384)
        at javax.mail.Service.connect(Service.java:297)
        at javax.mail.Service.connect(Service.java:156)
        at javax.mail.Service.connect(Service.java:105)
        at javax.mail.Transport.send0(Transport.java:168)
        at javax.mail.Transport.send(Transport.java:98)
        at org.apache.jsp.testEmail_jsp.sendMail(testEmail_jsp.java:90)
        at org.apache.jsp.testEmail_jsp._jspService(testEmail_jsp.java:173)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:957)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:745)
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
        at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1949)
        at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:302)
        at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:296)
        at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1509)
        at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:216)
        at sun.security.ssl.Handshaker.processLoop(Handshaker.java:979)
        at sun.security.ssl.Handshaker.process_record(Handshaker.java:914)
        at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1062)
        at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
        at sun.security.ssl.SSLSocketImpl.writeRecord(SSLSocketImpl.java:747)
        at sun.security.ssl.AppOutputStream.write(AppOutputStream.java:123)
        at com.sun.mail.util.TraceOutputStream.write(TraceOutputStream.java:101)
        at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
        at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
        at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1418)
        ... 36 more
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:387)
        at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
        at sun.security.validator.Validator.validate(Validator.java:260)
        at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:324)
        at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)
        at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:124)
        at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1491)
        ... 47 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:141)
        at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:126)
        at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
        at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:382)
        ... 53 more
problem in sendmail****************** javax.mail.MessagingException: Can't send command to SMTP host;
  nested exception is:
        javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
2017-01-12/14:48:33.282 DEBUG: resourcepool.BasicResourcePool - Checking for expired resources - Thu Jan 12 14:48:33 IST 2017 [com.mchange.v2.resourcepool.BasicResourcePool@4b1228f]