Couldn't wait till next week ... I did not manage to find the root cause. Too many nested ELResolvers, MockRequests and so on. Still don't know from where the problem arises. Everything I saw was ThreadLocal. But I think I managed to work around this (this time for real) using a plain old Java synchronized() around the renderer call (synchronizing on some static member, of course). Perhaps not the legal J2EE way, but might be acceptable since it's detached using @Asynchronous. Now every single mail is arriving as expected ... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4119271#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...