webmail recebe e não envia

Feb 20 00:31:45 webmail postfix/smtp[24994]: 978BC70F00: to=<jbm5688@gmail.com>, relay=none, delay=20, delays=0.06/0.01/20/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=gmail.com type=MX: Host not found, try again)

no envio ele da esse erro!!!

Grato pelas dicas...