The goal is to check if an email might be acceptable or not. For that you need to combine the response values that are important to you. Here is an example response:

{
    "email": "mail@domain.com",
    "valid": true, // Email correctly formatted accordingly to RFC rules
    "disposable": true, // Belongs to a disposable email service
    "mx_records": true, // Has MX records, migth have emails associated with it
    "exists": null // Connects to SMTP to check if the account exists (null means SMTP wasn't reached)
}

A good indicator if the email exist or not is to evaluate the mx_records. If it’s false, the email doesn’t exist

In PHP, you can use something like this:

if ($response->valid && !$response->disposable && $response->mx_records && ($response->exists === null || $response->exists)) {
    // there is an high chance of the email being reachable
}