Windows Server - No recibo correo

Hola comunidad, tengo el sig. problema: en un servidor 2003 tengo un dns que me da salida a internet con la sig. configuracion

Name Type Data
(same as parent folder) Start of Authority (SOA) [2007042713], dns.midominio.com.mx., root.midominio.com.mx.
(same as parent folder) Name Server (NS) dns.midominio.com.mx.
(same as parent folder) Name Server (NS) mail.midominio.com.mx.
(same as parent folder) Host (A) 200.xxx.xxx.xxx
(same as parent folder) Mail Exchanger (MX) [10] smtp.midominio.com.mx.
(same as parent folder) Mail Exchanger (MX) [9] midominio.com.mx.
(same as parent folder) Text (TXT) v=spf1 mx ptr -all
dns Host (A) 200.xxx.xxx.xxx
mail Host (A) 200.xxx.xxx.xxx
root Responsible Person (RP) postmaster.midominio.com.mx.
smtp Host (A) 200.xxx.xxx.xxx
smtp Text (TXT) v=spf1 mx -all
www Host (A) 200.xxx.xxx.xxx

y un servidor de correo con linux y postfix

el problema es que no recibo correo de hotmail, de otros sitios si, pero de hotmail no. Si puedo enviar correos a hotmail. Cuando envio de hotmail me manda el siguente error.

Reporting-MTA: dns;bay0-omc2-s29.bay0.hotmail.com
Received-From-MTA: dns;BAY107-W28
Arrival-Date: Fri, 7 Mar 2008 08:15:33 -0800

Final-Recipient: rfc822;[email protected]
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;554 Transaction Failed (1022769381:189:-2147467259)

Gracias de antemano