Captcha or recaptcha is good enough imo, no point in reinventing the wheel.
Alternatively, split instructions in an email and on the website. For ex:
Send email with
What is the square of 3 (sent as an image for every word)
And on the website
Email + 25 = xxxxx
Captcha or recaptcha is good enough imo, no point in reinventing the wheel. Alternatively, split instructions in an email and on the website. For ex: Send email with What is the square of 3 (sent as an image for every word) And on the website Email + 25 = xxxxx