From the examples currently shown in jndi-resources-howto.html, one might assume that adding "foo.bar.baz" will be added to the java.util.Properties object passed-into the Session.getInstance method, but it is not entirely clear. It would be nice to explicitly state that arbitrary <Resource> attributes will be converted into Session configuration properties. Also, there are certain properties that are outside of the JavaMail spec, such as "password".
Fixed in 7.0.x and will be included in 7.07. onwards.