protected void storeToken(final RequestContext requestContext, final CasSimpleMultifactorAuthenticationTicket token) throws Throwable {
        multifactorAuthenticationService.store(token);
        WebUtils.addInfoMessageToContext(requestContext, MESSAGE_MFA_TOKEN_SENT);
        MultifactorAuthenticationWebflowUtils.putSimpleMultifactorAuthenticationToken(requestContext, token);
    }
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