setup:
apache 1.3.20
php 4.0.6 (announced it self as 4.0.5 in phpinfo?)
php.ini:
 SMTP = linux
 sendmail_from = w2k@windows

p.php:
<?
 print("foobar");
 mail (
   "user1@linux, root@linux,",
   "test subject",
   "test mailer\n",
   "From: WebMaster <webmaster@linux>\nx-header: php mailer\nTo: User One <user1@linux>, root <root@linux>\nCc: user2@linux\n"
 );
?>

calling it failed and leads to
error.log:
FATAL:  emalloc():  Unable to allocate -86918290 bytes

so long.