If you want to let your visitors send greeting cards from your website, try wp-greet a greeting card plugin for WordPress.
wp-greet uses the plugin NextGenGallery to manage the greetingcards. wp-greet offers several options to avoid spam and to keep spambots from using your greetingcards as spam mail. wp-greet supports the plugins Captcha!, where a captcha code has to be entered before sending a card, or the Math Comment Spam Protection Plugin, where a simple sum has to be calculated. You can choose between various workflows to process the greeting card requests.
You can find more information reading the english documentation of wp-greet