def convert(self, value, param, ctx):
        """ Validate value using regexp. """
        rxp = '^[^@]+?@[-.a-z0-9]+$'
        regex = re.compile(rxp, re.I)
        try:
            if regex.match(value):
                value = value.split("@")
                return value
            else:
                self.fail('%s is not a valid email address' % value, param,
                          ctx)
        except ValueError:
            self.fail('%s is not a valid email address' % value, param, ctx)
Validate value using regexp.