public void setRequireAuth(final boolean requireAuth) {
        this.requireAuth = requireAuth;
    }
@param requireAuth true for mandatory smtp authentication, i.e. no mail mail
                   be accepted until authentication succeeds. Don't forget to
                   set AuthenticationHandlerFactory to allow client
                   authentication. Defaults to false.
src/main/java/de/gessnerfl/fakesmtp/smtp/server/BaseSmtpServer.java