Using the mail activity in a process definition does not work as soon as the process is deployed to the jBPM installation on Tomcat. The mail activity works fine in a unit test. The following exception is thrown when the execution reaches the mail activity:

Caused by: javax.mail.NoSuchProviderException: smtp
at javax.mail.Session.getService(Session.java:794)
at javax.mail.Session.getTransport(Session.java:718)
at javax.mail.Session.getTransport(Session.java:661)
at javax.mail.Session.getTransport(Session.java:641)
at javax.mail.Session.getTransport(Session.java:696)
at org.jbpm.pvm.internal.email.impl.MailSessionImpl.send(MailSessionImpl
.java:48)