For use this plugin with send e-mail form (for example - "feedback" or "contact us" form on your site for anonymous users), you need to create view with form with some of next field (field "Body" is required):
This sample view for send "contact us" form: (online-demo sample)
<div class="common-form">
<h5 class="title">
Contact us</h5>
@if (ViewData["ReCaptchaFormResult"] == "Mail was sent")
{
<p style="color: green;">
<strong>Thank you for feedback! Your message was save.</strong></p>
}
<form method="post" action="">
@Html.AntiForgeryToken()
<!-- this contact form will send an email to the email address defined in system/settings/smtp-->
@*<input type="hidden" name="RedirectUrl" value='@Url.FrontUrl().PageUrl("Thankyou")'/>*@
<input type="hidden" name="recaptcha_form_action" value='SENDEMAIL' /><!-- SENDEMAIL or ADDCONTENT -->
<table>
<tbody>
@*<tr>
<th>
<label for="from">
From email:</label>
</th>
<td>
<input type="text" id="from" name="From" data-val-required="From is required" data-val="true"
data-val-regex-pattern = "\b[a-zA-Z0-9._%\-+']+@@[a-zA-Z0-9._\-]+\.[a-zA-Z]{2,6}\b"
data-val-regex = "Not valid e-mail." />
@Html.ValidationMessageForInput("From")
</td>
</tr>
<tr>
<th>
<label for="subject">
Subject:</label>
</th>
<td>
<input type="text" id="subject" name="Subject" />
</td>
</tr>*@
<tr>
<th>
<label for="body">
Body:</label>
</th>
<td>
<textarea id="body" name="Body" cols="20" rows="10" data-val-required="Body is required"
data-val="true"></textarea>
@Html.ValidationMessageForInput("Body")
</td>
</tr>
<tr>
<th>
<label for="contact_name">
Contact name:</label>
</th>
<td>
<input type="text" id="contact_name" name="contact_name" />
</td>
</tr>
<tr>
<th>
<label for="contact_email">
Contact e-mail:</label>
</th>
<td>
<input type="text" id="contact_email" name="contact_email" />
</td>
</tr>
<tr>
<th>
<label for="contact_phone">
Contact phone:</label>
</th>
<td>
<input type="text" id="contact_phone" name="contact_phone" />
</td>
</tr>
<tr>
<th>
<label for="contact_address">
Contact address:</label>
</th>
<td>
<input type="text" id="contact_address" name="contact_address" />
</td>
</tr>
<tr>
<th>
<label for="contact_firm">
Firm name:</label>
</th>
<td>
<input type="text" id="contact_firm" name="contact_firm" />
</td>
</tr>
<tr>
<th>
Code:
</th>
<td>
@if (ViewData["ReCaptchaSuccess"] != null && !(bool)ViewData["ReCaptchaSuccess"])
{
<strong><span style="color: red;">Captcha Validation FAILED!</span></strong>
}
@Html.Raw((string)ViewData["ReCaptchaScript"])
</td>
</tr>
<tr>
<th>
</th>
<td>
<input type="submit" name="submit" value="submit" /><br />
</td>
</tr>
</tbody>
</table>
</form>
</div>
Also you need to add this plugin on your view:
ReCaptcha plugin return next values: