Technical details of permanent failure: Google tried to deliver your message, but it was rejected by the server for the recipient domain rtggroupusa.com by mx.zoho.com. [165.254.167.50].The error that the other server returned was:553 Relaying disallowed

I set up a free account for email which was working fine until I set up a second free account for a different domain. As soon as I updated the MX, the original account was unable to receive emails and I was not able to send or receive emails between the two accounts.

Am I doing something that can't be done or am I setting up something wrong?

Both domains are registered at Godaddy under the same account. I am only needing two emails for each domain.