Email notification failed with error: javax.mail.MessagingException: Could not convert socket to TLS in Windchill PDMLink

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)

• In BGMS logs

  DEBUG [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage submit message
  2025-04-07 15:44:12,543 DEBUG [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage   locale: it
  2025-04-07 15:44:12,543 DEBUG [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage  subject: Approve Promotion Request
  2025-04-07 15:44:12,544 DEBUG [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage     from: [email protected]
  2025-04-07 15:44:13,390 INFO  [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage message submission failed
  2025-04-07 15:44:13,390 INFO  [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage Could not convert socket to TLS
  2025-04-07 15:44:13,390 INFO  [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage subject: Approve Promotion Request
  2025-04-07 15:44:13,390 INFO  [EMailQueue.SchedulingThread] wt.mail.EMailMessage wcadmin - EMailMessage not submitted to: [email protected]
  2025-04-07 15:44:13,391 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - jakarta.mail.MessagingException: Could not convert socket to TLS;
  2025-04-07 15:44:13,391 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin -   nested exception is:
  2025-04-07 15:44:13,391 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	java.io.IOException: Can't verify identity of server: win2019mail.debemsrl.local
  2025-04-07 15:44:13,391 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at org.eclipse.angus.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:2173)
  2025-04-07 15:44:13,391 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at org.eclipse.angus.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:741)
  2025-04-07 15:44:13,391 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at jakarta.mail.Service.connect(Service.java:345)
  2025-04-07 15:44:13,392 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at com.infoengine.webject.msg.SendMail.invoke(SendMail.java:261)
  2025-04-07 15:44:13,392 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at com.infoengine.procunit.webject.WebjectProcessor.invokeWebject(WebjectProcessor.java:624)
  2025-04-07 15:44:13,392 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at com.infoengine.procunit.webject.WebjectProcessor.processTask(WebjectProcessor.java:210)
  2025-04-07 15:44:13,392 INFO  [EMailQueue.SchedulingThread] wt.system.err wcadmin - 	at com.infoengine.SAK.Webject.invoke(Webject.java:492)