Unable to send mail to hotmail from rackspace cloud

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http://serverfault.com – I'm having issue sending mail from postfix on a rackspace cloud instance for my domain. Hotmail says "550 SC-001 (SNT0-MC4-F35) Unfortunately, messages from 198.101.x.x weren't sent. Please contact your Internet service provider since part of their network is on our block list. " Here is the mail log Sep 20 08:02:59 mydomain postfix/smtpd[1810]: disconnect from localhost[] Sep 20 08:02:59 mydomain postfix/smtp[1814]: 59CFF4B191: to=<[email protected]>, relay=mx3.hotmail.com[]:25, delay=0.19, delays=0.1/0.01/0.06/0.01, dsn=5.0.0, status=bounced (host mx3.hotmail. (HowTos)