PHP and mail(); - RH9: ok, FC1: fail, FC3: fail - what a damn problem is here ??

[M.Clasen]

Hi, this is really confusing me ...

Server 1:
- RH9
- kabel dialup, dynamic IP
- provider 1&1 1und1.de

Server 2:
- FC3
- kabel dialup, dynamic IP 
- provider german T-Com t-online.de

Server 3:
- FC1
- 100MBit synchron, static IP
- provider fasthousing.de Server in datacenter serverhousing

Testmailscript (testmail.php):
---------------------------------------------------------------
<?

$headers 	= "From: rawfox at isti542.fasthousing.de";
$empfaenger 	= "webmaster at hg-carstyling.de";
$betreff	= "Testmail from testmail.php";
$eintrag	= "Testmail Eintrag von variabel eintrag; from testmail.php";

echo "Empfaenger:$empfaenger <br>
  	 Betref: $betreff <br>
	 Eintrag: $eintrag <br>
	 Headers: $headers <br><br>
";
mail($empfaenger, $betreff, $eintrag, $headers);
echo "E-Mail an ".$empfaenger." wurde versendet <br>";

?>
---------------------------------------------------------------
Server 1 passes the test fine, Server 2+3 fail the test.
All machines are rpm-based and yum-updated.
There is no special exotic configuration on the machines, but only the
RH9 distro is able to mail out and got the mailprocess logged
in /var/log/maillog ?!

What im doing wrong ?

greetings from germany :)

M.Clasen