The problem with matching against the fully fledged RFC compliant regex is that not all email addresses are RFC compliant. As I indicated in my comment above, I've abondoned trying to "correctly" or "completely" validate email addresses. There's onyl one thing certain in an email address: it contains the "@" character.
One cellular phone company in Japan used to allow people to register e-mail addresses with two periods in a row before the @ character. I have seen some addresses like this in the wild, but the decision to mark these as valid or not for an app depends on the domain you're working in. At my old job making web apps for Japanese companies, programmers would usually allow these types of addresses if we were making a mobile site.
