I am getting this error with email connector when testing with an outlook email.

2018-06-27 16:59:30,536 [WorkManager.WebSphere_EJB_Container_AsynchMethods_Internal_WorkManager : 3] EmailConnector WARN - EmailConnector-3.4.0.0.340003 - connect: could not connect to [address=smtp-mail.outlook.com, smtps=false, login=testuser_123456@outlook.com, pwd=***]
javax.mail.MessagingException: Can't send command to SMTP host;
nested exception is:
javax.net.ssl.SSLHandshakeException: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1717)
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1704)
at com.sun.mail.smtp.SMTPTransport.ehlo(SMTPTransport.java:1088)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:468)
at javax.mail.Service.connect(Service.java:291)
at javax.mail.Service.connect(Service.java:172)
at com.avaya.zephyr.services.emailconnector.hosts.EmailHost.connect(EmailHost.java:160)
at com.avaya.zephyr.services.emailconnector.connectionpool.ConnectionPool.getConnection(ConnectionPool.java:78)
at com.avaya.zephyr.services.emailconnector.OutboxDrainer.drainOutbox(OutboxDrainer.java:54)
at sun.reflect.GeneratedMethodAccessor511.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
at java.lang.reflect.Method.invoke(Method.java:508)
at com.ibm.ejs.container.AsyncMethodWorkWrapper.run(AsyncMethodWorkWrapper.java:234)
at com.ibm.ws.asynchbeans.J2EEContext.run(J2EEContext.java:811)
at com.ibm.ws.asynchbeans.WorkWithExecutionContextImpl.go(WorkWithExecutionContextImpl.java:222)
at com.ibm.ws.asynchbeans.ABWorkItemImpl.run(ABWorkItemImpl.java:206)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1892)
Caused by: javax.net.ssl.SSLHandshakeException: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.jsse2.j.a(j.java:31)
at com.ibm.jsse2.as.a(as.java:262)
at com.ibm.jsse2.C.a(C.java:515)
at com.ibm.jsse2.C.a(C.java:11)
at com.ibm.jsse2.D.a(D.java:720)
at com.ibm.jsse2.D.a(D.java:635)
at com.ibm.jsse2.C.r(C.java:44)
at com.ibm.jsse2.C.a(C.java:184)
at com.ibm.jsse2.as.a(as.java:481)
at com.ibm.jsse2.as.i(as.java:130)
at com.ibm.jsse2.as.a(as.java:497)
at com.ibm.jsse2.h.write(h.java:23)
at com.sun.mail.util.TraceOutputStream.write(TraceOutputStream.java:110)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:93)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:151)
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1715)
... 16 more
Caused by: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.jsse2.util.f.a(f.java:21)
at com.ibm.jsse2.util.f.b(f.java:51)
at com.ibm.jsse2.util.e.a(e.java:19)
at com.ibm.jsse2.aA.a(aA.java:204)
at com.ibm.jsse2.aA.a(aA.java:160)
at com.ibm.jsse2.aA.checkServerTrusted(aA.java:207)
at com.ibm.jsse2.D.a(D.java:67)
... 27 more
Caused by: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.PKIXCertPathBuilderImpl.engineBuild(PKIXCertPathBuilderImpl.java:422)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268)
at com.ibm.jsse2.util.f.a(f.java:153)
... 33 more
Caused by: java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.BasicChecker.<init>(BasicChecker.java:111)
at com.ibm.security.cert.PKIXCertPathValidatorImpl.engineValidate(PKIXCertPathValidatorImpl.java:199)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.myValidator(PKIXCertPathBuilderImpl.java:749)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.buildCertPath(PKIXCertPathBuilderImpl.java:661)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.buildCertPath(PKIXCertPathBuilderImpl.java:607)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.engineBuild(PKIXCertPathBuilderImpl.java:368)
... 35 more
Caused by: java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.CertPathUtil.findIssuer(CertPathUtil.java:316)
at com.ibm.security.cert.BasicChecker.<init>(BasicChecker.java:108)
... 40 more
@

Caused by: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.jsse2.util.f.a(f.java:21)
at com.ibm.jsse2.util.f.b(f.java:51)
at com.ibm.jsse2.util.e.a(e.java:19)
at com.ibm.jsse2.aA.a(aA.java:204)
at com.ibm.jsse2.aA.a(aA.java:160)
at com.ibm.jsse2.aA.checkServerTrusted(aA.java:207)
at com.ibm.jsse2.D.a(D.java:67)
... 27 more
Caused by: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.PKIXCertPathBuilderImpl.engineBuild(PKIXCertPathBuilderImpl.java:422)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268)
at com.ibm.jsse2.util.f.a(f.java:153)
... 33 more
Caused by: java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.BasicChecker.<init>(BasicChecker.java:111)
at com.ibm.security.cert.PKIXCertPathValidatorImpl.engineValidate(PKIXCertPathValidatorImpl.java:199)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.myValidator(PKIXCertPathBuilderImpl.java:749)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.buildCertPath(PKIXCertPathBuilderImpl.java:661)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.buildCertPath(PKIXCertPathBuilderImpl.java:607)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.engineBuild(PKIXCertPathBuilderImpl.java:368)
... 35 more
Caused by: java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.CertPathUtil.findIssuer(CertPathUtil.java:316)
at com.ibm.security.cert.BasicChecker.<init>(BasicChecker.java:108)
... 40 more
2018-06-27 16:59:30,536 [WorkManager.WebSphere_EJB_Container_AsynchMethods_Internal_WorkManager : 3] EmailConnector WARN - EmailConnector-3.4.0.0.340003 - connect: could not connect to [address=smtp-mail.outlook.com, smtps=false, login=test123456@outlook.com, pwd=***]
javax.mail.MessagingException: Can't send command to SMTP host;
nested exception is:
javax.net.ssl.SSLHandshakeException: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1717)
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1704)
at com.sun.mail.smtp.SMTPTransport.ehlo(SMTPTransport.java:1088)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:468)
at javax.mail.Service.connect(Service.java:291)
at javax.mail.Service.connect(Service.java:172)
at com.avaya.zephyr.services.emailconnector.hosts.EmailHost.connect(EmailHost.java:160)
at com.avaya.zephyr.services.emailconnector.connectionpool.ConnectionPool.getConnection(ConnectionPool.java:78)
at com.avaya.zephyr.services.emailconnector.OutboxDrainer.drainOutbox(OutboxDrainer.java:54)
at sun.reflect.GeneratedMethodAccessor511.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
at java.lang.reflect.Method.invoke(Method.java:508)
at com.ibm.ejs.container.AsyncMethodWorkWrapper.run(AsyncMethodWorkWrapper.java:234)
at com.ibm.ws.asynchbeans.J2EEContext.run(J2EEContext.java:811)
at com.ibm.ws.asynchbeans.WorkWithExecutionContextImpl.go(WorkWithExecutionContextImpl.java:222)
at com.ibm.ws.asynchbeans.ABWorkItemImpl.run(ABWorkItemImpl.java:206)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1892)
Caused by: javax.net.ssl.SSLHandshakeException: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.jsse2.j.a(j.java:31)
at com.ibm.jsse2.as.a(as.java:262)
at com.ibm.jsse2.C.a(C.java:515)
at com.ibm.jsse2.C.a(C.java:11)
at com.ibm.jsse2.D.a(D.java:720)
at com.ibm.jsse2.D.a(D.java:635)
at com.ibm.jsse2.C.r(C.java:44)
at com.ibm.jsse2.C.a(C.java:184)
at com.ibm.jsse2.as.a(as.java:481)
at com.ibm.jsse2.as.i(as.java:130)
at com.ibm.jsse2.as.a(as.java:497)
at com.ibm.jsse2.h.write(h.java:23)
at com.sun.mail.util.TraceOutputStream.write(TraceOutputStream.java:110)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:93)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:151)
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1715)
... 16 more
Caused by: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.jsse2.util.f.a(f.java:21)
at com.ibm.jsse2.util.f.b(f.java:51)
at com.ibm.jsse2.util.e.a(e.java:19)
at com.ibm.jsse2.aA.a(aA.java:204)
at com.ibm.jsse2.aA.a(aA.java:160)
at com.ibm.jsse2.aA.checkServerTrusted(aA.java:207)
at com.ibm.jsse2.D.a(D.java:67)

at com.ibm.jsse2.as.a(as.java:497)
at com.ibm.jsse2.h.write(h.java:23)
at com.sun.mail.util.TraceOutputStream.write(TraceOutputStream.java:110)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:93)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:151)
at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1715)
... 16 more
Caused by: com.ibm.jsse2.util.h: PKIX path building failed: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.jsse2.util.f.a(f.java:21)
at com.ibm.jsse2.util.f.b(f.java:51)
at com.ibm.jsse2.util.e.a(e.java:19)
at com.ibm.jsse2.aA.a(aA.java:204)
at com.ibm.jsse2.aA.a(aA.java:160)
at com.ibm.jsse2.aA.checkServerTrusted(aA.java:207)
at com.ibm.jsse2.D.a(D.java:67)
... 27 more
Caused by: java.security.cert.CertPathBuilderException: PKIXCertPathBuilderImpl could not build a valid CertPath.; internal cause is:
java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.PKIXCertPathBuilderImpl.engineBuild(PKIXCertPathBuilderImpl.java:422)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268)
at com.ibm.jsse2.util.f.a(f.java:153)
... 33 more
Caused by: java.security.cert.CertPathValidatorException: The certificate issued by CN=DigiCert Global Root CA, OU=www.digicert.com, O=DigiCert Inc, C=US is not trusted; internal cause is:
java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.BasicChecker.<init>(BasicChecker.java:111)
at com.ibm.security.cert.PKIXCertPathValidatorImpl.engineValidate(PKIXCertPathValidatorImpl.java:199)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.myValidator(PKIXCertPathBuilderImpl.java:749)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.buildCertPath(PKIXCertPathBuilderImpl.java:661)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.buildCertPath(PKIXCertPathBuilderImpl.java:607)
at com.ibm.security.cert.PKIXCertPathBuilderImpl.engineBuild(PKIXCertPathBuilderImpl.java:368)
... 35 more
Caused by: java.security.cert.CertPathValidatorException: Certificate chaining error
at com.ibm.security.cert.CertPathUtil.findIssuer(CertPathUtil.java:316)
at com.ibm.security.cert.BasicChecker.<init>(BasicChecker.java:108)
... 40 more
2018-06-27 16:59:30,538 [WorkManager.WebSphere_EJB_Container_AsynchMethods_Internal_WorkManager : 10] EmailConnector INFO - EmailConnector-3.4.0.0.340003 - EmailConnector(3.4.0.0.340003) - no host or not connected, returning request to outbox
2018-06-27 16:59:30,540 [WorkManager.WebSphere_EJB_Container_AsynchMethods_Internal_WorkManager : 4] EmailConnector INFO - EmailConnector-3.4.0.0.340003 - EmailConnector(3.4.0.0.340003) - no host or not connected, returning request to outbox
2018-06-27 16:59:30,540 [WorkManager.WebSphere_EJB_Container_AsynchMethods_Internal_WorkManager : 3] EmailConnector INFO - EmailConnector-3.4.0.0.340003 - EmailConnector(3.4.0.0.340003) - no host or not connected, returning request to outbox
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found the answer here
https://www.devconnectprogram.com/forums/posts/list/20309.page#p146063

Great! Thanks for letting us know.