src/Rules/EmailTrait.php
private function validateEmail($value)
    {
        $isValid = filter_var($value, FILTER_VALIDATE_EMAIL);
        if ($isValid === false) {
            $this->throwInvalidArgumentMustBe("valid email");
        }
    }
private function validateEmail($value)
    {
        $isValid = filter_var($value, FILTER_VALIDATE_EMAIL);
        if ($isValid === false) {
            $this->throwInvalidArgumentMustBe("valid email");
        }
    }
"I found some addresses that FILTER_VALIDATE_EMAIL rejects, but RFC5321 permits"
http://php.net/manual/en/function.filter-var.php#112492

@param $value