Tarpitting slows down email validation.
It’s a service on a mail server of the email address(es), we’re trying to validate that slows down responses to our inbound validation request to the mail server. Tarpitting is a defence mechanism, created as a defence against inbound attacks on a network.
The idea is to make a network an unattractive target for email spamming and computer hackers. The server will respond, but very slowly. It’s called tarpitting because it’s sticky, slows things down and isn’t pleasant.
We can validate emails that are tarpitted via CORE service because that service is designed to process over time and will obey instructions to revisit servers that ask us to ‘come back later’.
Our MORE Realtime API is a more speed-oriented service that carries out a fast, single check so that won’t revisit tarpitting servers and will instead return a result of ‘unverifiable’.