Failed to deliver the emails, began today

We have used normal emails for the domain @ hotprintind.com.br.

Today, two hours ago began to give problem in sending the emails, the error message that appears is:

  DOMAIN_NOT_RESOLVED

This message appears for any domain, I already tested the domains and they are ok.

It seems to be a problem on the zoho server.

Thanks for any help you can give me.