mail problem

[Emmanuel Petit]

I apologise in advance for my little knowledges in php.
I use PHP 5.2.1
Here is an extract of the script which causes me problems.

//email of recipient
$e*********@som esite.com';

//tracking email to the webmaster of the site
$d************@ testsite.com';
mail($dd, 'Activation',$d etails, 'From: ad************@ testsite.com');

//prepar the body of the mail
$body = $name . ',';
$body .= "\n\nThank you for activating your account:\n\n\n" ;
$body .="http://www.testsite.co m/fr/activation.php? x=$ts";
$body .= "\n\nSee you soon on www.testsite.co m.";

//send the mail
mail($ea, 'Mail activation',$bo dy, 'From: ad************@ testsite.com');

//second tracking email to webmaster of the site
$details="Mail sent to $ea";
mail('w******** @testsite.com', 'Activation',$d etails, 'From:
ad************@ testsite.com');

Okay.
The problem :
I create a test user, fill out all the details giving one of my email
adress, on my own PC (but doing it on the live web site NOT IN LOCAL),
and click the activate button on the form. The script runs perfectly,
and after a few second I get the email in my mail box with the
activation link.
In the webmaster mailbox, I get the two tracking email. So far, so good.

Now, the webmaster create a user. This user on a different machine (two
users in differents places tried and had the problem), goes through the
same activation process, fills in his email address, and click the
activate button. He never receives his activation mail, but the
webmaster still gets the two tracking mails.

I tried on different machines, with different users, without success.
Can someone help me?

thank you.