$pattern = '/[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})/';

$filePath = '/tmp/rty/avril_2016.csv';
$fileArr = file($filePath);

foreach ($fileArr as $k => $line) {
    $snum = preg_match($pattern, $line);
    if (!$snum)
    {
        var_dump($line);
        unset($fileArr[$k]);
    }
}