In order to protect YMCA Website Services customers, we have added anti-spam protection based on CAPTCHA and Google reCAPTCHA out of the box in YMCA Website Services core
You can check the tutorial for how to install and configure reCaptcha on your site.
In the majority of cases having the above configuration in place will protect you from 99% of spam, unless there is human-entered spam that has no protection. To overcome some human-based spam you should use blacklist logic for blocking email domains, used in spam messages.
For that, you can use the Protected Submissions module module, which allows you to harden all submissions on a site with a list of stop words as well as per-language settings.
Virtual Y use case
In order to overcome caching issues, Virtual Y uses the simple_recaptcha module which could be used in similar cases.
The CAPTCHA + reCAPTCHA module solution has presented some reliability issues. The most recent discussion and fix from drupal.org has also not reliably resolved issues for some clients.
At some point, the “Simple reCaptcha” module was used on a project and had no issues, so we’ve started to replace the “CAPTCHA” + “reCAPTCHA” modules with “Simple reCAPTCHA”.