We had been working on adding an IDN addon domain in cPanel and received invalid domain name.
Internationalized domain name – Wikipedia
An internationalized domain name (IDN) is an Internet domain name that contains at least one label that is displayed in software applications, in whole or in part, in a language-specific script or alphabet
Domain cannot be added directly in cPanel because domain contains at least one label
Domain Name : lamé.com
We need to use below converter to convert the IDN to ASCII
Unicode url/domain: lamé.com
ASCII/Punycode (ACE) : xn--lam-dma.com
Once domain is converted in ASC can be added in cPanel.