Envio correo OK pero no recibo(log no sale nada)

[Piradoxlanieve]

nose cual es el motivo pero .dobrainformatica.com apunta a esa ip sino ha otra llevo ya mas de 24horas y no me la cambia sin embargo hago ping y va ha la ip buena como puedo configurar el postfix para que no apunte a .dobrainformatica.com sino a mail.dobrainformatica.com tengo cambiado el main.cf pero nada el intenta mandar a dobrainformatica.com
This is the mail system at host universohosting.net.

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<dobrainformatica@dobrainformatica.com>: host
dobrainformatica.com[213.186.33.5] said: 550 sorry, no mailbox here by that
name (#5.1.1) (in reply to RCPT TO command)