Magento is Zend Framework based e-commerce platform. Sure, Zend Framework is not in active development phase, because developers are in progress with new framework – Zend Framework 2 or shortly ZF2. That’s why sometimes Magento can slip up when interact with something new. For ex., new domains.
Let’s check this case – domain validation for e-mail address verification. Any new domains like .company or .ninja will be unaccepted by Magento.
How fix it? Just copy /lib/Zend/Validate/Hostname.php into /app/code/core/Zend/Validate/Hostname.php Afterwards, replace $_validTlds array in this file with new data, which you can retrieve from here: http://www.iana.org/domains/root/db