Does anyone know of any specific headers Hotmail looks for in order to decide whether emails are spam or not?

I am using;

[php]
$headers = "From: UserAdministration\r\n";
$headers .= "Content-type: text/plain\r\n";
$headers .= "MIME-Version: 1.0\r\n";
mail($to, $subject, $message, $headers);
[/php]

But none of my messages are getting through. Is there any specific reason why?

I capture headers with this IE Toolbar addon: IE HTTP Headers

It shows the headers sent and recieved so you should be able to send yourself blocked and unblock mail to a Hotmail account and check for the difference... FWIW: Firefox probably has an extension for this as well...

.....Willy

I believe Hotmail uses a service called Bonded Sender which replaced their whitelist feature a while back. WHat used to happen was that if a legitimate email was getting blocked you could apply to be put on the whitelist and if it was genuine it would be added, and then allowed through. These days, with Bonded Sender, you have to put down a "guarantee" to ensure that your email gets through. Only problem is this "bond" is a couple of grand and theres no way to get around it. What should please you is that AOL are thinking of bringing in a similar system, although that will be a per-mail charge.

To me it sounds like a high tech protection racket for email.

Thanks for the link Willy, I think I'll try that.

Good info Si, seems extortionate to me. Emails should be free, we pay monthly for the internet connection so everything that comes with that package should be free!