Description:
------------
Some weird (but still perfectly valid) e-mail addresses are rejected by filter_var with FILTER_VALIDATE_EMAIL filter.
I've got sample data from https://en.wikipedia.org/wiki/Email_address#Valid_email_addresses

While support for comments was mention before I was unable to find any references to spaces.

Test script:
---------------
$emails = array(
    'test@example.com',
    'test.derp@example.com',
    'test+nick@example.com',
    'abc."defghi".xyz@example.com',
    '"abcdefghixyz"@example.com',
    'jsmith@[192.168.2.1]',
    'jsmith@[IPv6:2001:db8::1]',
'long.but.still.perfectly.valid.email.address@on.even.longer.domain.name.owned.by.some.weird.name.company.which.name.you.cannot.pronounce.com',
    'other.email-with-dash@example.com',
    '"much.more unusual"@example.com',
    '"very.unusual.@.unusual.com"@example.com',
    '"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com',
    'admin@mailserver1 (local domain name with no TLD)',
    '#!$%&\'*+-/=?^_`{}|~@example.org',
    '"()<>[]:,;@\\\"!#$%&\'*+-/=?^_`{}| ~.a"@example.org',
    '" "@example.org (space between the quotes)',
    '☃☃☃@example.com (Unicode characters in local part)',
    '☃☃☃@☃☃☃.com (Unicode characters in domain part)',
    'new@domain.pizza'
);

foreach ($emails as $email) {
    echo (filter_var($email, FILTER_VALIDATE_EMAIL)) ? 
        "[+] Email $email is valid\n" : 
        "[-] Email $email is NOT valid\n";
}

Actual result:
--------------
http://3v4l.org/qTsVc