Emails not being accepted by Outlook/Hotmail servers (550 SC-002 namespace mining)

Email from our server is not being accepted by certain Microsoft mail servers. I have joined the Smart Network Data Services and the JMRP but it has not provided any useful information. I have submitted calls via https://support.live.com/eform.aspx but it has not provided any other additional information other than we are still engaging in namespace mining.

Check the sending log files and concentrate on logs that are sending to nonexistent @hotmail.com, @live.com, @msn.com, @outlook.com?with multiple tries and failures.

I don't see how as we have not been able to send email for the past two weeks. I am also confused why some servers will accept mail and others will reject.

Bounce mail

mx1.hotmail.com
mx2.hotmail.com
mx3.hotmail.com
mx4.hotmail.com

Accept mail

*.blu0.hotmail.com
*.col0.hotmail.com
*.dub0.hotmail.com
*.snt0.hotmail.com

Hopefully somebody can help shed some light on the problem.

Thanks