Since may 11 TLD's (top-level domain names) have been added. In order for this to work successfully, a lot of applications will have to be fixed. Many email-validation scripts might use [a regular expression] approach [to match most address formats].

Unfortunately, this approach will only continue to work with the normal ASCII-based domain names. He includes a list of several that could break it including ones in Chinese, Korean, Persian, Russian and Arabic. He recommends a very liberal regular expression (one that allows for "punycode" strings) to check the email, find the record and try to find an MX record on that domain.