hotmail blacklist and rDNS questions

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http://serverfault.com – My company has recently purchased a VPS for email and webhosting. I am not an expert on email authentication but here is my story. After the VPS was purchased we started receiving bouncebacks with the error message from hotmail.com ]: 550 SC-001 (COL0-MC1-F10) Unfortunately, messages from weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors After doing research on the issue I have tried to join hotmail Sender ID program. I also a (HowTos)