I searched and I can't find the solution to this. Basically, external emails (Yahoo) received this error when sending to firstname.lastname@example.org. This domain hosted outside Godaddy. It used to work before.
If you still need help with this, I recommend reaching out to our live support team via phone or chat for further assistance. I've seen similar errors that are generally part of a threshold bounce that our email team would need to investigate directly to help resolve.