docs: @Reference(service = MailSessionRegistrar.class,
                      policy = ReferencePolicy.DYNAMIC,
                      cardinality = ReferenceCardinality.OPTIONAL,
                      target = "(component.name=com.ibm.ws.javamail.management.j2ee.MailSessionRegistrarImpl)")
      protected void setMailSessionRegistrar(ServiceReference<MailSessionRegistrar> ref) {
          mailSessionRegistrarRef.setReference(ref);
          registerJavaMailMBean();
      }