My solution to this would be to charge a small amount (say $0.01) to send an email to someone not in your contacts. You pay a dollar to onboard to the service,

My solution to this would be to charge a small amount (say $0.01) to send an email to someone not in your contacts. You pay a dollar to onboard to the service, and each time you send an email to a random person it would charge a penny. If you receive a reply the penny is refunded (presumably because they were interested enough). This works because it breaks the economics of spam. If one in a million people fall for your $1000 scam, that’s a profit of $0.001/email. Thats ok if emails cost nothing to send. But if they cost $0.01 to send, it doesn’t make sense to send them.