protected List<String> findSelectedSmsRecipients(final RequestContext requestContext, final Principal principal) {
        val recipients = getSmsRecipients(requestContext);
        return findSelectedRecipients(requestContext, recipients);
    }
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