Anti-Spam filter proplem.

I've been trying to send an email to a freind but every time I send the email I get a reply from [email protected] stating the following:

This is an automatically generated Delivery Status Notification. Delivery to the following recipients failed.

there is also an attachment that says:

Reporting-MTA: dns;blu0-omc2-s35.blu0.hotmail.com
Received-From-MTA: dns;BLU135-W53
Arrival-Date: Sun, 21 Dec 2008 05:35:06 -0800

Final-Recipient: rfc822;[email protected]
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;554 This email is rejected. It contains keywords rejected by the antispam content filter. PLEASE ADVISE YOUR RECIPIENT OF THIS REJECTION.

any help would be appreciated. thanks