sou novo no Digital ocean e tenho um área de hospedagem e minha área de email não recebe nem envia emails, fica dando erro
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

helena@cubodigitalbrasil.com.br
all hosts for ‘cubodigitalbrasil.com.br’ have been failing for a long time (and retry time not reached)
Reporting-MTA: dns; host.cubodigitalhost.com.br

Action: failed
Final-Recipient: rfc822;helena@cubodigitalbrasil.com.br
Status: 5.0.0
o que pode ser?