The API results also provide all the details around the email address if you want to know the metadata around an email address.
Please note that all details can either be true, false or null. Null values mean checks could not be run for that particular detail due to other dependent checks.
The email address follows proper formatting as specified in RFC822 Section 6.1
The domain of the email address contains proper MX records
The MX records can be connected to through SMTP or RFC5321
The domain you're trying to contact employs an inbox which accepts all email addresses also known as "catch-all". This is an anti-spam technique which makes it difficult to validate email addresses properly.
The domain is a known disposable email service which anyone can use to accept email without needing a real email account, also known as "temporary emails"
The domain is known service that provides a free email service like Yahoo or Gmail
The email server responded in a manner which is known to be a spam trap
The email server properly accepts email for the given email address and responded accordingly
The email server employs an anti-spam technique which makes validating emails slow. You may want to use webhooks to validate email addresses which employ greylisting.
This uses HTTP methods to identify if they have valid accounts with certain services (e.g. Yahoo)
Is this a known email proxy service. Email proxies are usually used to filter emails.