Yes, and good luck using a search engine to find 月山＠何でも.jp or الله@gmail.com By the way, the first one is not a mail address as ＠ and @ are different characte

Yes, and good luck using a search engine to find 月山＠何でも.jp or الله@gmail.com By the way, the first one is not a mail address as ＠ and @ are different characters. But actually it may be because ＠ is the @ in the Japanese character set. So it probably should be accepted right? How about if I use the Japanese ＠ in a korean address? Is that valid? Or a likely attack? Also in the Arabic name, the first character of the string is the one closer to the @ (it reads right to left), be sure to take that into account in a search interface. I think it is totally utopian to think that a programmer can know all the subtleties of all the writing systems in the world. I agree that this is a problem that needs to be solved, but users and UX designers should in no way underestimate the magnitudes of additional work it causes.