Lo más importante es revisar las siguientes líneas de configuración

# SASL SUPPORT FOR CLIENTS

# The following options set parameters needed by Postfix to enable 

# Cyrus-SASL support for authentication of mail clients. 

# 

smtpd_sasl_auth_enable = yes

smtpd_sasl_security_options = noanonymous

smtpd_sasl_local_domain = $myhostname

broken_sasl_auth_clients = yes

... 

smtpd_recipient_restrictions = 

   permit_sasl_authenticated, 

   permit_mynetworks, 

   check_relay_domains

El contenido está en inglés, pero resulta bastante útil. 

Error Codes:

# 550 SC-001 Mail rejected by Microsoft  for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help.

# 550 SC-002 Mail rejected by Microsoft  for policy reasons. The mail server IP connecting to Hotmail has exhibited namespace mining behavior. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help.

# 550 SC-003 Mail rejected by Microsoft  for policy reasons. Your IP address appears to be an open proxy/relay. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help.

# 550 SC-004 Mail rejected by Microsoft for policy reasons. A block has been placed against your IP address because we have received complaints concerning mail coming from that IP address. We recommend enrolling in our Junk E-Mail Reporting Program (JMRP), a free program intended to help senders remove unwanted recipients from their e-mail list. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help.

# 550 DY-001 Mail rejected by Microsoft  for policy reasons. We generally do not accept email from dynamic IP's as they are not typically used to deliver unauthenticated SMTP e-mail to an Internet mail server. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help. http://www.spamhaus.org maintains lists of dynamic and residential IP addresses.

# 550 DY-002 Mail rejected by Microsoft  for policy reasons. The likely cause is a compromised or virus infected server/personal computer. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help.

# 550 OU-001 Mail rejected by Microsoft  for policy reasons. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help. For more information about this block and to request removal please go to: http://www.spamhaus.org.

# 550 OU-002 Mail rejected by Microsoft for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation. If you are not an e-mail/network admin please contact your E-mail/Internet Service Provider for help.

# 421 RP-001 The mail server IP connecting to Microsoft  server has exceeded the rate limit allowed. 
Reason for rate limitation is related to 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 (state 13). 

# 220 SNT0-MC3-F28.Snt0.hotmail.com Sending unsolicited commercial or bulk e-mail to Microsoft's computer network is prohibited.

Other restrictions are found at http://privacy.msn.com/Anti-spam/.
Violations will result in use of equipment located in California and other states.

If you are a customer using the 3rd party email service or a Microsoft Account user who is unable to receive emails from a particular 3rd party domain:

Contact your domain administrator and ask them to get in touch with the Microsoft Sender Support Team. They have to fill out the e-form that can be found on the following link:

https://support.live.com/eform.aspx?productKey=edfsmsbl3&ct=eformts&wa

If you do not know how you can get in touch with your domain admin, you can use WHOIS tools to search for your contact e-mail address of your domain admin.

If you are the 3rd party Domain Administrator:

Please review our policies and guidelines at http://postmaster.live.com.

If you are in compliance, submit a support request to our Email and Delivery Filtering Services team by clicking on the link to the e-form under the troubleshooting section in the postmaster site mentioned above.