validMailbox returns null

[kakopappa]

first of all, great work guys.

For some reason, for some email addresses, validMailbox returns null.

here is an example

const EmailValidator = require('email-deep-validator');
 const emailValidator = new EmailValidator();

const start = async () => {
    const { wellFormed, validDomain, validMailbox } = await emailValidator.verify('robyorkspam@yorktaxservicecom');
    console.log(wellFormed, validDomain, validMailbox);
}

start();

[kakopappa]

should have read the readme