protected Event buildSuccessEvent(final CasSimpleMultifactorAuthenticationTicket token) {
        val attributes = new LocalAttributeMap<Object>("token", token.getId());
        return eventFactory.event(this, CasWebflowConstants.TRANSITION_ID_SUCCESS, attributes);
    }
Event attribute to allow registration of email.
support/cas-server-support-simple-mfa-core/src/main/java/org/apereo/cas/mfa/simple/web/flow/CasSimpleMultifactorSendTokenAction.java