6.8. Symphony fails sending email: PKIX path building failed

Symptoms

Symphony displays the following error:

Unable to send emails - Communication error - sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target 

Background

This caused by a change in new Java libraries.

Solution

Update Java:

Stop Symphony (or stop service if configured to run as a service)

Go to Control Panel and uninstall all instances of Java

Go to Java.com and select 'Download' in the main title bar:

Select 'See all Java downloads':

Select 'Windows Offline':

Install that version and then re-launch Symphony (or start the service if configured to run as a service)