Erro de envio de e-mail

Seguinte,
Quando envio e-mail para alguns dominios, aparece isso.

Jan 4 08:48:27 mail postfix/smtp[10494]: A3D752835A: to=<USUARIO@DOMINIO>, relay=DOMINIO[IP], delay=37, status=bounced (host DOMINIO[IP] said: 550-Verification failed for <MEU USUARIO@MEU DOMINIO> 550-The mail server could not deliver mail to MEU USUARIO@MEU DOMINIO. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. 550 Sender verify failed (in reply to RCPT TO command))



Onde esta o problema, comigo ou com os outros dominios????

Att