Not able to send emails to hotmail email ids

hi guys ,
When i try to send a email to hotmail it is bouncing back with following error message.

host mx4.hotmail.com [65.55.37.72]: 550 SC-001 Mail rejected by Windows Live Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems. If you are not an email/network admin please contact your E-mail/Internet Service Provider for help. Email/network admins, please visit http://postmaster.live.com for email delivery information and support

I had raised a ticket with hotmail and hotmail replied back saying that they didnt block our domain.

Pls help how can get rid of these problem.

Thanks in advance.

Kiran.