Q: "sun.security.validator.ValidatorException: No trusted certificate found" error message when connecting gmail

A: The error is due to Java not trusting the certificate from GMail. Newer version of JVM solve the problem. Ruben Suarez provides a solution for those cannot upgrade:

To solve the problem you must add gmail server certificate to the default cacerts keystore of the jre.

To do that follow these:

That's it. Now your can login to your account ^_^

Thanks Ruben!