public boolean performNoSuchUserCheck() {
        return true;
    }
RFC 6121 8.5.1. "No Such User" specifies how the server must respond to a request made against a non-existing user.

The abstract IQ Handler plugin can act accordingly, but allows implementations to override this behavior. By
default, Openfire will perform a non-existing user check and act according to the RFC 6121. Subclasses can
disable this behavior by overriding this method, and returning 'false'.

@return 'true' if the Abstract IQ Handler implementation should detect if the IQ request is made against a non-existing user and return an error.
@see <a href="http://xmpp.org/rfcs/rfc6121.html#rules-localpart-nosuchuser">RFC 6121 8.5.1. "No Such User"</a>
@see <a href="https://igniterealtime.atlassian.net/jira/software/c/projects/OF/issues/OF-880">OF-880</a>
xmppserver/src/main/java/org/jivesoftware/openfire/handler/IQHandler.java