When you open an incident and release the email using a Flex Response rule you got an error:
FlexResponse Action Failed
[Email Quarantine Connect Approve Action] failed with message: 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
The error is due to the wrong certificate configured in Brightmail.
Please login to the Brightmail Control Center and verify the HTTPS certificate. See screenshot attached.