電子メール通知が次のエラーで失敗しました: javax.mail.MessagingException: Windchill PDMLink でソケットを TLS に変換できませんでした

ERROR [wt.jmx.core.mbeans.Emailer.mailer] wt.jmx.core.mbeans.Emailer  - Attempt to send mail failed [Id=150; Subject='Queue Problems']
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:366)
	at wt.jmx.core.mbeans.Emailer$SendEmailTask.sendMessage(Emailer.java:1492)
	at wt.jmx.core.mbeans.Emailer$SendEmailTask.run(Emailer.java:1303)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
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:1964)
	at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:328)
	at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:322)
	at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1614)
	at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:216)
	at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1052)
	at sun.security.ssl.Handshaker.process_record(Handshaker.java:987)
	at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1072)
	at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1385)
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1413)
	at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1397)
	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)