Odd Lucee Mail error(s)

[Tim Bugler]

I'm having an odd issue with two of my Lucee servers. I have mail set up using an open smtp port 25 server, but I continually get what appears to be SSL errors. We're not using SSL; SSL and TLS are NOT selected in the mail set up. The error details are below:

 Can't send command to SMTP host;
  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.sendCommand(SMTPTransport.java:1365):1365
	at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1353):1353
	at com.sun.mail.smtp.SMTPTransport.ehlo(SMTPTransport.java:794):794
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:336):336
	at javax.mail.Service.connect(Service.java:236):236
	at lucee.runtime.net.smtp.SMTPSender.run(SMTPSender.java:58):58
:0
	at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1365):1365
	at com.sun.mail.smtp.SMTPTransport.sendCommand(SMTPTransport.java:1353):1353
	at com.sun.mail.smtp.SMTPTransport.ehlo(SMTPTransport.java:794):794
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:336):336
	at javax.mail.Service.connect(Service.java:236):236
	at lucee.runtime.net.smtp.SMTPSender.run(SMTPSender.java:58):58

Any Ideas?

Apache 2.4.* / Lucee 4.5.2.018

Thanks

T.

[Tim Bugler]

Should also mention it is not random, not every email fails.