It might have to do with the UseJBossWebLoader setting in jboss-web.deployer/META-INF/jboss-service.xml Once this is set to true, pietemartin's error appears. Once this is set to false, asynchronous mails can be sent just fine. Setting this to false, however, breaks much of the RichFaces functionality like, for example, passing any rich UI object between the web layer and the Seam Bean layer (which leads to the dreaded ClassCastException). So does anyone of you know how it might be possible to use the JBoss unified class loader together with asynchronous mails? Or to tell me if this is desirable? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4112635#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...