This page documents the RECAPTCHA_PRIVATE_KEY configuration setting in FormMail.
Type Of Setting
RECAPTCHA_PRIVATE_KEY is an OPTIONAL setting, which means...
OPTIONAL : you can change this setting if you need to, but the default value is fine for most circumstances.
Enables use of reCaptcha.
Set RECAPTCHA_PRIVATE_KEY to your private key when you've subscribed to the reCaptcha service. The private key is also called the "secret key" in reCaptcha version 2.
The reCaptcha service provides you with a public key and a private key. The public key goes into your HTML form.
The private or secret key goes into this setting so that FormMail can validate the user's CAPTCHA response.
$RECAPTCHA_PRIVATE_KEY = "";
$RECAPTCHA_PRIVATE_KEY = "6Ld_5QkAXKAAAGyHeOrOIhJzF2tl4LHWx54iB-S2";