jysafe

CN: 最基本的形式： 
 输入上图物质分子式，看着复杂，其实挺简单的，数数各个原子个数，按照顺序堆起来就行了。 
 此外还有计算矩阵、说出事件发生日期的验证码，三者随机出现。
EN: This is a special captcha plugin. 
 It is not verified by math but by chemical formula and Calculation matrix and date of some event.

Traum Captcha

Inboxify

Inboxify is an online application for sending email newsletters. Many companies, mostly from the Netherlands, make use of Inboxify for sending newsletters to their customers and relations. At the moment, Inboxify is only available in Dutch.
With the Inboxify Sign Up Form plugin you can add sign up forms and checkboxes to your WordPress website to enable your visitors to sign up directly to your Inboxify list.
<h4>Features</h4>
<ul>
<li>Easy to use Sign Up Form Widget</li>
<li>Add a sign up form to your posts and pages using the shortcode [inboxify_subscribe]</li>
<li>Add a subscribe checkbox to your comment form, registration form or user profile form</li>
<li>Prevent spam submissions using one of the supported CAPTCHA plugins</li>
<li>Compatible with the “Really Simple CAPTCHA”, “SI CAPTCHA Anti-Spam” and “WordPress ReCaptcha Integration” plugins</li>
<li>AJAX form processing</li>
</ul>

Inboxify Sign Up Form

Easily add Inboxify newsletter sign up forms to your WordPress website with the offical Inboxify Sign Up Form plugin.

Traum Captcha vs Inboxify Sign Up Form