keytool -import -file "C:UsersmartinDocumentsAutomation ProjectsRemedySOAPWebServicesrcresourcesmail.cer" -keystore "C:Program Files (x86)Javajdk1.8.0_121jrelibsecuritycacerts" -alias mail

java.lang.RuntimeException: javax.mail.MessagingException: Could not convert socket to TLS;
  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 src.RemedySOAPWebService.sendEmail(RemedySOAPWebService.java:137)
    at src.RemedySOAPWebService.printSOAPResponse(RemedySOAPWebService.java:237)
    at src.RemedySOAPWebService.lambda$main$0(RemedySOAPWebService.java:77)
    at java.util.ArrayList.forEach(ArrayList.java:1249)
    at src.RemedySOAPWebService.main(RemedySOAPWebService.java:49)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: javax.mail.MessagingException: Could not convert socket to TLS;
  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.startTLS(SMTPTransport.java:2064)
    at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:724)
    at javax.mail.Service.connect(Service.java:388)
    at javax.mail.Service.connect(Service.java:246)
    at javax.mail.Service.connect(Service.java:195)
    at javax.mail.Transport.send0(Transport.java:254)
    at javax.mail.Transport.send(Transport.java:124)
    at src.RemedySOAPWebService.sendEmail(RemedySOAPWebService.java:134)
    ... 9 more
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:1514)
    at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:216)
    at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1026)
    at sun.security.ssl.Handshaker.process_record(Handshaker.java:961)
    at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1062)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1403)
    at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1387)
    at com.sun.mail.util.SocketFetcher.configureSSLSocket(SocketFetcher.java:598)
    at com.sun.mail.util.SocketFetcher.startTLS(SocketFetcher.java:525)
    at com.sun.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:2059)
    ... 16 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:1496)
    ... 26 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)
    ... 32 more

Trust this certificate? [no]:  yes
Certificate was added to keystore

public static void sendEmail(List<String> incidentNumberList, String assignedGroup) {
        final String username = "martin";
        final String password = "pass123!";

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "internetsmtp.martin.com");
        props.put("mail.smtp.port", "25");

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

        try {
            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("martin@martin.com"));
            message.setRecipients(Message.RecipientType.TO,
                    InternetAddress.parse("martin@martin.com"));
            message.setSubject("Remedy Tickets — Attention Needed");
            message.setText("Assigned Group: " + assignedGroup + "n" + "Priority: " + "Critical" + "nnThe following remedy tickets need your attention:nn" + incidentNumberList.toString());

            Transport.send(message);

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }