I'm able to send emails to/from Zoho accounts and send from them, but I'm not able to receive from others.

I'm able to send emails to/from Zoho accounts and send from them, but I'm not able to receive from others.

I'm able to send emails to/from Zoho accounts and send from them, but I'm not able to receive from others.

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain phcdc.org by smtp.secureserver.net. [68.178.213.203].

The error that the other server returned was:
550 5.1.1 <admin@phcdc.org> Recipient not found.  <http://x.co/irbounce>

I've also followed the directions for the MX records, but it's still not working.  HELP.