I use a plugin to Aperture to send mail to gmail. It was failing due to a
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 plugin author (plugin home page) found the following utility:
http://blogs.sun.com/andreas/entry/no_more_unable_to_find