path

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:1907)
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:666)
	at javax.mail.Service.connect(Service.java:345)
	at javax.mail.Service.connect(Service.java:226)
	at EbayWebparser.sendEmail(EbayWebparser.java:172)
	at EbayWebparser.main(EbayWebparser.java:62)
	at __SHELL6.run(__SHELL6.java:6)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at bluej.runtime.ExecServer$3.run(ExecServer.java:725)
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:1902)
	at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:276)
	at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:270)
	at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1338)
	at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:154)
	at sun.security.ssl.Handshaker.processLoop(Handshaker.java:868)
	at sun.security.ssl.Handshaker.process_record(Handshaker.java:804)
	at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1032)
	at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1328)
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1355)
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1339)
	at com.sun.mail.util.SocketFetcher.configureSSLSocket(SocketFetcher.java:528)
	at com.sun.mail.util.SocketFetcher.startTLS(SocketFetcher.java:465)
	at com.sun.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:1902)
	... 11 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:385)
	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:326)
	at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:231)
	at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:126)
	at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1320)
	... 21 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
	at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:196)
	at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268)
	at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:380)
	... 27 more