$body = \'This is a test\';
$subject = \'Confirmation\';
$headers = \'From: Testing Site\' . \"\\r\\n\";
$headers .= \'Reply-To: admin@myserver.com\' . \"\\r\\n\
If you're using WordPress, you can look up plugin for Hotmail/Outlook friendly emailing capability.
However if it is a standalone script you might wanna look into Microsoft's official answer to this query on the URL : http://answers.microsoft.com/en-us/outlook_com/forum/oemail-osend/why-are-the-emails-sent-to-microsoft-account/b64e3e4a-0d93-40c8-8e28-4be849012f9c
In-short Email-Server provider has to fill this form (once) : https://support.live.com/eform.aspx?productKey=edfsmsbl3&ct=eformts&wa=wsignin1.0&scrx=1
In order to get their emails accepted by Hotmail/Outlook.