That's it, it's a very different problem. I've found plenty of info about how to avoid SPAM on the contact-us form but I can't use it to solve my problem. A good option would be to add reCaptcha when new users register on the store , but I couldn't find a forum thread with precise info or a free module to achieve that.
There's a free module that works on PS 1.6 but not on 1.7. It's this one, in case it's useful for somebody: https://prestapros.com/en/blog/free-module-recaptcha-for-prestashop-registration-form
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That's it, it's a very different problem. I've found plenty of info about how to avoid SPAM on the contact-us form but I can't use it to solve my problem. A good option would be to add reCaptcha when new users register on the store , but I couldn't find a forum thread with precise info or a free module to achieve that.