Contact form loop

I try to use
that plugin but don’t work correctly

if i put correct data a mail is send correctly without a messagge like
“mail send correctly”

and if i put wrong data no one error messagge is visible.

What will be the problem?

that is the link

http://www.tesorosanpietro.it/wp/?page_id=5

that is the code

<div class="cf-box">
	<p class="cf-field cf-first">Nome
		[text* your-name] </p>

	<p class="cf-field">Email
		[email* your-email] </p>

	<p class="cf-field cf-full">Messaggio
		[textarea your-message] </p>
[captchac captcha-644 size:m]
[captchar captcha-644]
	<p class="cf-submit">[submit "Invia messaggio"]</p>
</div>

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thanks

http://wordpress.org/plugins/really-simple-captcha/