I built this for my company email, but instead of sending captchas it puts non-customer emails into a folder that I never read. Emails from customers and contacts get into my inbox, and get labeled based on their support subscription level.
Most tech companies I've seen gate and filter customer support on web not email, then only sales and external interfacing employees need external emails and the bigger problem is phishing not spam.
For my personal email I would never use this, because I myself would never solve a captcha to reach someone's inbox and I can't expect different from others.