Thank you for contacting Windows Live Hotmail Domain Support. My name is Paul and I will be assisting you.
I gather that you experiencing mail deliverability issues and receive the error “550 Mail rejected by Windows Live Hotmail for policy reasons”. I understand how this concerns you. Let me help you out.
We have identified that messages from your IP (126.96.36.199) are being blocked based on the recommendations of Symantec’s Brightmail filters, as traffic/email originating from your IP matched characteristics of recent spam attacks from compromised, or ‘zombie’ infected, machines.
After reviewing the information you provided, we have taken steps to remove the block. This change should take effect within the next 24-48 hours. Be aware that Symantec will continue to run checks against your IP to ensure that the vulnerabilities have been removed. The block can be reapplied until the problem is fully addressed.
In order to prevent this and future exploits of this nature, please verify that your MTAs (Mail Transfer Agents/Mail Servers) are under your full control, have not been compromised, and that you are not unwittingly sending any spam. We also suggest that you scan your computer to verify that there is no malicious software installed. You can obtain a free Windows Server or client PC scan by visiting http://safety.live.com or http://www.microsoft.com/athome/security/downloads/default.mspx
More information about this exploit can be found here: http://antivirus.about.com/od/whatisavirus/a/zombiepc.htm
You can also find additional information on common deliverability questions by reviewing the resources at http://postmaster.live.com
The troubleshooting steps in this email are recommendations only. Microsoft makes no guarantees that following these steps will guarantee deliverability to MSN, Windows Live Hotmail, or Live.com customers.
Windows Live Hotmail Domain Support