Description:
------------
Setup:

- Mailhog
- SSMTP
- Configured php.ini to ssmtp -t

Execute the test script with 7.4 and 8.0. The email looks correct in 7.4 and its totally broken on 8.0. The headers are in the body in PHP 8.0.

Test script:
---------------
$to      = 'nobody@example.com';
        $subject = 'the subject';
        $message = 'hello';
        $headers = 'From: webmaster@example.com' . "\r\n" .
            'Reply-To: webmaster@example.com' . "\r\n" .
            'X-Mailer: PHP/' . phpversion();

        mail($to, $subject, $message, $headers);

Taken from https://www.php.net/manual/en/function.mail

Expected result:
----------------
The mail is the same on both PHP versions

Actual result:
--------------
It's totally different. The PHP 8.0 doesn't have a subject. I guess it has something done with https://github.com/php/php-src/commit/6983ae751cd301886c966b84367fc7aaa1273b2d#diff-c6922cd89f6f75912eb377833ca1eddb7dd41de088be821024b8a0e340fed3df