I've got a Magento site running and need to enter new customers that use the new .club domain. When you enter a .club in the Email field, you cannot save them as it error's with invalid email address.
Which version of Magento are you using?
I've tried with 18.104.22.168 and is possible to register a customer with a .club domain:
I understand that the email is validated by Zend_Validate_EmailAddress and, internally, Zend_Validate_Hostname validates the hostname part of the email.
The club tlds is present on that version too.
Have you some custom validation or some override for Mage_Customer module?