Any kind of technical email validation is horribly unreliable at best and there is no chance that this GitHub repo is going to work any better. As a result the

Any kind of technical email validation is horribly unreliable at best and there is no chance that this GitHub repo is going to work any better. As a result the only place such a service is useful is for someone who has a ton of low-value emails they don’t trust, and they don’t want a ton of bounces when they hit send (which risks losing your send privileges with pretty much high-volume email platform). So they run all their emails through a service like this, and only send to the ones marked valid. This excludes a ton of emails that actually are valid, but failed the check (false negatives). But that’s ok because the emails were low-value to begin with. If this sounds like a spammy operation… bingo. Technical email validation services are really only useful for people who are doing things like buying email lists from commercial providers, harvesting emails from sites like HN, or forcing people to enter an email address to do basic things with a free service.