Unrecognized SSL message, plaintext connection?

public class JavaMailTest1 {
	public static void main(String[] args) throws MessagingException {
		Properties props = new Properties();
		props.setProperty("mail.debug", "true");
		props.setProperty("mail.smtp.auth", "true");
		props.setProperty("mail.transport.protocol", "smtp");
		
		// SSL
		props.setProperty("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
		props.setProperty("mail.smtp.socketFactory.fallback", "false");
		props.setProperty("mail.smtp.port", "465");
		props.setProperty("mail.smtp.socketFactory.port", "465");
		
		Session session = Session.getInstance(props);
		
		Message msg = new MimeMessage(session);
		msg.setText("你好吗？");
		msg.setFrom(new InternetAddress("发件箱地址"));
		
		Transport transport = session.getTransport();
		transport.connect("smtp.sina.com", "用户名", "密码");
		transport.sendMessage(msg, new Address[] {new InternetAddress("收件箱地址")});
		transport.close();
	}
}

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.openServer(SMTPTransport.java:1972)
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:642)
	at javax.mail.Service.connect(Service.java:295)
	at javax.mail.Service.connect(Service.java:176)

/*
 * Copyright 2006 Sun Microsystems, Inc.  All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/**
 * http://blogs.sun.com/andreas/resource/InstallCert.java
 * Use:
 * java InstallCert hostname
 * Example:
 *% java InstallCert ecc.fedora.redhat.com
 */

import javax.net.ssl.*;
import java.io.*;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

/**
 * Class used to add the server's certificate to the KeyStore
 * with your trusted certificates.
 */
public class InstallCert {

    public static void main(String[] args) throws Exception {
        String host;
        int port;
        char[] passphrase;
        if ((args.length == 1) || (args.length == 2)) {
            String[] c = args[0].split(":");
            host = c[0];
            port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
            String p = (args.length == 1) ? "changeit" : args[1];
            passphrase = p.toCharArray();
        } else {
            System.out.println("Usage: java InstallCert [:port] [passphrase]");
            return;
        }

        File file = new File("jssecacerts");
        if (file.isFile() == false) {
            char SEP = File.separatorChar;
            File dir = new File(System.getProperty("java.home") + SEP
                    + "lib" + SEP + "security");
            file = new File(dir, "jssecacerts");
            if (file.isFile() == false) {
                file = new File(dir, "cacerts");
            }
        }
        System.out.println("Loading KeyStore " + file + "...");
        InputStream in = new FileInputStream(file);
        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
        ks.load(in, passphrase);
        in.close();

        SSLContext context = SSLContext.getInstance("TLS");
        TrustManagerFactory tmf =
                TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
        tmf.init(ks);
        X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];
        SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
        context.init(null, new TrustManager[]{tm}, null);
        SSLSocketFactory factory = context.getSocketFactory();

        System.out.println("Opening connection to " + host + ":" + port + "...");
        SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
        socket.setSoTimeout(10000);
        try {
            System.out.println("Starting SSL handshake...");
            socket.startHandshake();
            socket.close();
            System.out.println();
            System.out.println("No errors, certificate is already trusted");
        } catch (SSLException e) {
            System.out.println();
            e.printStackTrace(System.out);
        }

        X509Certificate[] chain = tm.chain;
        if (chain == null) {
            System.out.println("Could not obtain server certificate chain");
            return;
        }

        BufferedReader reader =
                new BufferedReader(new InputStreamReader(System.in));

        System.out.println();
        System.out.println("Server sent " + chain.length + " certificate(s):");
        System.out.println();
        MessageDigest sha1 = MessageDigest.getInstance("SHA1");
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        for (int i = 0; i < chain.length; i++) {
            X509Certificate cert = chain[i];
            System.out.println
                    (" " + (i + 1) + " Subject " + cert.getSubjectDN());
            System.out.println("   Issuer  " + cert.getIssuerDN());
            sha1.update(cert.getEncoded());
            System.out.println("   sha1    " + toHexString(sha1.digest()));
            md5.update(cert.getEncoded());
            System.out.println("   md5     " + toHexString(md5.digest()));
            System.out.println();
        }

        System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");
        String line = reader.readLine().trim();
        int k;
        try {
            k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;
        } catch (NumberFormatException e) {
            System.out.println("KeyStore not changed");
            return;
        }

        X509Certificate cert = chain[k];
        String alias = host + "-" + (k + 1);
        ks.setCertificateEntry(alias, cert);

        OutputStream out = new FileOutputStream("jssecacerts");
        ks.store(out, passphrase);
        out.close();

        System.out.println();
        System.out.println(cert);
        System.out.println();
        System.out.println
                ("Added certificate to keystore 'jssecacerts' using alias '"
                        + alias + "'");
    }

    private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();

    private static String toHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 3);
        for (int b : bytes) {
            b &= 0xff;
            sb.append(HEXDIGITS[b >> 4]);
            sb.append(HEXDIGITS[b & 15]);
            sb.append(' ');
        }
        return sb.toString();
    }

    private static class SavingTrustManager implements X509TrustManager {

        private final X509TrustManager tm;
        private X509Certificate[] chain;

        SavingTrustManager(X509TrustManager tm) {
            this.tm = tm;
        }

        public X509Certificate[] getAcceptedIssuers() {
            throw new UnsupportedOperationException();
        }

        public void checkClientTrusted(X509Certificate[] chain, String authType)
                throws CertificateException {
            throw new UnsupportedOperationException();
        }

        public void checkServerTrusted(X509Certificate[] chain, String authType)
                throws CertificateException {
            this.chain = chain;
            tm.checkServerTrusted(chain, authType);
        }
    }

}

Loading KeyStore C:\Program Files\Java\jre7\lib\security\cacerts...
Opening connection to smtp.sina.com:465...
Starting SSL handshake...

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(Unknown Source)
        at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
        at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
        at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
        at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
        at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
        at sun.security.ssl.Handshaker.processLoop(Unknown Source)
        at sun.security.ssl.Handshaker.process_record(Unknown Source)
        at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
        at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
        at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
        at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
        at InstallCert.main(InstallCert.java:97)
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(Unknown Source)
        at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
        at sun.security.validator.Validator.validate(Unknown Source)
        at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source)
        at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
        at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
        at InstallCert$SavingTrustManager.checkServerTrusted(InstallCert.java:192)
        at sun.security.ssl.AbstractTrustManagerWrapper.checkServerTrusted(Unknown Source)
        ... 9 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
        at java.security.cert.CertPathBuilder.build(Unknown Source)
        ... 17 more

Server sent 1 certificate(s):

 1 Subject CN=*.sina.com, O="Sina.com Technology(China)Co.,ltd", L=Beijing, ST=Beijing, C=CN, SERIALNUMBER=mL/iTnzl-0Pr1rH-6U2RZH/h3zFjZxoK
   Issuer  CN=GeoTrust SSL CA, O="GeoTrust, Inc.", C=US
   sha1    43 a9 5b bc 9b 86 85 99 e3 21 63 af b0 09 78 4a 67 25 d7 a1
   md5     90 c2 45 da 67 68 cd c2 44 56 21 ef ed c6 6b 5e

Enter certificate to add to trusted keystore or 'q' to quit: [1]

Protocol	Store or	Uses	Supports
Name		Transport?	SSL?	STARTTLS?
-------------------------------------------------
imap		Store		No	    Yes
imaps		Store		Yes	    N/A
pop3		Store		No	    Yes
pop3s		Store		Yes	    N/A
smtp		Transport	No	    Yes
smtps		Transport	Yes	    N/A

public class JavaMailTest1 {
	public static void main(String[] args) throws MessagingException {
		Properties props = new Properties();
		props.setProperty("mail.debug", "true");
		props.setProperty("mail.smtp.auth", "true");
		
		// 协议名称设置为smtps，会使用SSL
		props.setProperty("mail.transport.protocol", "smtps");
		
		Session session = Session.getInstance(props);
		
		Message msg = new MimeMessage(session);
		msg.setText("你好吗？");
		msg.setFrom(new InternetAddress("发件箱地址"));
		
		Transport transport = session.getTransport();
		transport.connect("smtp.sina.com", "用户名", "密码");
		transport.sendMessage(msg, new Address[] {new InternetAddress("收件箱地址")});
		transport.close();
	}
}