I did ask on the EJB3 forum, but eventually worked it out on my own. The problem is that there is no stack trace. I don't have eclipse open atm, but basically the JBoss code catches all exceptions, wraps them in an EJBException, but doesn't include the root exception, just it's msg. So you never get access to the stack trace. I'm going to file a JIRA bug on it, as it makes diagnosing this sort of thing almost impossible. I had to go into my code and catch NPE and log it myself, just so I could see the stack trace. Turns out some e-mail was getting delivered based on an optional x-original-to header, with a null to: header, which blew an NPE, since I had assumed that incoming e-mail would have a to address. It ended up being my code's fault, but the error message not only didn't indicate that at all, but also didn't provide a stack trace or other useful into, so it took a while to track down. Sorry if my posts seemed a bit panicy, but with the amount of traffic I was getting, each time it broke, the forums got lots of negative comments, etc... Thanks. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3989804#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...