For example those two:
filter_var('[email protected]', FILTER_VALIDATE_EMAIL);
filter_var('lornajaneaaaaaa[email protected]', FILTER_VALIDATE_EMAIL);

In 5.2.10 they will be good. In 5.2.17 they will give false (the same with 5.4). I dont know in which version behavior changed. However that's the reason why I have trust issues in filter_var() for validating email (if i dont know on which version it will run i cant predict he outcome).