You can use your own mail session by implementing the org.jbpm.pvm.internal.email.spi.MailSession interface and leaving out the <mail-session /> tag in your jbpm.cfg.xml, instead provide a <object class="your.own.MailSessionImpl"> each time a mail needs to be send the MailSession.send(Collection<Message> emails) method will be called and you can do whatever you want with the emails. Extending jBPM4's MailSessionImpl is a bit more tricky, you somehow need to inject the mailServers as far as i can tell, best take a look at the MailSessionBinding to check how this can be done.