Email validation for exotic characters

It seems that the email validation in Grails just apply a simple regex. While it validates most emails, some exotic but authorized characters will make the validation fail.

The German ß character for example is used in some email addresses, but won't pass the grail validation:

package com.stuff.user.AppUser

import grails.test.mixin.Mock
import spock.lang.Specification

/**
 * Created by hschoonjans on 21/03/2016.
 */
@Mock(AppUser)
class AppUserSpec extends Specification {

    def "It doesn't validate an email with an eszett"() {
        given:
        AppUser user = new AppUser(email: "helainß@hotmail.com")

        expect:
        !user.validate(["email"])
    }
}

Using a custom regex for validation, authorizing the ß would be trivial but what if a user tries to use another exotic yet valid character in his mail address?

To avoid this problem, I would like to know what Java/Groovy/Grails universal email address validator exist. A class/regex that would validate any valid email address, smarter than the current Grails email validation.

I've come across this several times before in my own Grails projects and I've had pretty good success using this RegEx:

/^((([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*)|((\x22)((((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(([\x01-\x08\x0b\x0c\x0e-\x1f\x7f]|\x21|[\x23-\x5b]|[\x5d-\x7e]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(\\([\x01-\x09\x0b\x0c\x0d-\x7f]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]))))*(((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(\x22)))@((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.?$/i