Java's email library sucks. You need to sumbit to the JavaMail way of looking at email to do the simplest thing with it. First you need to understand that JavaMail is 'cross-platform' in the sense that it's for any hypothetical messaging system, not just email. So it has layers and layers of lame abstractions. Lots of configuration needed to do the simplest things.

That's one of the worst examples, but my overall feeling is that dynamic languages on the JVM aren't worth it. You're probably better off with an independent language environment.