This is Gateway :
=================
[root@gateway-pmx ~]# grep D5E22103BFBC: /var/log/maillog
Nov 23 18:30:03 gateway-pmx postfix/smtpd[23736]: D5E22103BFBC: client=localhost.localdomain[127.0.0.1]
Nov 23 18:30:03 gateway-pmx postfix/cleanup[23090]: D5E22103BFBC: message-id=<844848-2200711523232854437@EMILIO>
Nov 23 18:30:03 gateway-pmx postfix/qmgr[27944]: D5E22103BFBC: from=<payos@bellsouth.net>, size=2733, nrcpt=1 (queue active)
Nov 23 18:30:04 gateway-pmx postfix/smtp[23267]: D5E22103BFBC: to=<mnavarro@miraflores.gob.pe>, relay=200.121.66.4[200.121.66.4]:25, delay=0.26, delays=0.1/0/0.11/0.04, dsn=4.3.0, status=deferred (host 200.121.66.4[200.121.66.4] said: 451 4.3.0 <mnavarro@miraflores.gob.pe>: Temporary lookup failure (in reply to RCPT TO command))

Nov 22 14:13:14 gateway-pmx postfix/smtpd[29319]: 3A0FB103BFC1: client=localhost.localdomain[127.0.0.1]
Nov 22 14:13:14 gateway-pmx postfix/cleanup[29096]: 3A0FB103BFC1: message-id=<C36B3EE3.6A53%jramirez@softmarkperu.com>
Nov 22 14:13:14 gateway-pmx postfix/qmgr[27944]: 3A0FB103BFC1: from=<jramirez@softmarkperu.com>, size=9250, nrcpt=1 (queue active)
Nov 22 14:13:14 gateway-pmx postfix/smtp[29320]: 3A0FB103BFC1: to=<?vdiaz@miraflores.gob.pe>, relay=200.121.66.4[200.121.66.4]:25, delay=0.26, delays=0.12/0/0.11/0.02, dsn=4.3.0, status=deferred (host 200.121.66.4[200.121.66.4] said: 451 4.3.0 < vdiaz@miraflores.gob.pe>: Temporary lookup failure (in reply to RCPT TO command))
Nov 22 14:36:06 gateway-pmx postfix/qmgr[27944]: 3A0FB103BFC1: from=<jramirez@softmarkperu.com>, size=9250, nrcpt=1 (queue active)
Nov 22 14:36:06 gateway-pmx postfix/smtp[30059]: 3A0FB103BFC1: to=<?vdiaz@miraflores.gob.pe>, relay=200.121.66.4[200.121.66.4]:25, delay=1373, delays=1372/0.01/0.13/0.07, dsn=4.3.0, status=deferred (host 200.121.66.4[200.121.66.4] said: 451 4.3.0 < vdiaz@miraflores.gob.pe>: Temporary lookup failure (in reply to RCPT TO command))


This is MTA :
?===========

Nov 23 18:49:30 snape postfix/smtpd[12396]: NOQUEUE: reject: RCPT from unknown[10.0.1.7]: 451 4.3.0 <    Contactosindirecci ndeemail???>: Temporary lookup failure; from=<biblioteca@miraflores.gob.pe> to=<??? Contactosindirecci?ndeemail???> proto=ESMTP helo=<bibliotecarp>
Nov 23 18:49:30 snape postfix/smtpd[12396]: > unknown[10.0.1.7]: 451 4.3.0 <    Contactosindirecci ndeemail???>: Temporary lookup failure
Nov 23 18:49:30 snape postfix/smtpd[12396]: > unknown[10.0.1.7]: 451 4.3.0 <    Contactosindirecci ndeemail???>: Temporary lookup failure