BoxTrapper CAPTCHA option for additional security

In addition to having the ability for sender's to reply or click to add themselves to the BoxTrapper whitelist, it would be great to have an option where both of these are replaced with a single option:

-Click a link to go to the cPanel site.

-At the site, complete a CAPTCHA to confirm addition to the whitelist.

Rationale: right now, it is possible for spammers to either manually click the link, manually reply to the link, or automatically do either. Generous estimate of spammers that do this: 1% to 5%.