如何在Javascript和PHP中验证非英语(UTF-8)编码的电子邮件地址?

Part of a website I am currently working on contains registration process where users have to provide their email address. Just recently I became aware that non-ascii based domains are possible (so is email). My backend is utf-8 encoded MySQL where I am expecting any users (with differnt locales) should be able to enter their email but don't know how to validate this kind of email address.Part of a website I am currently working on con