Unable to send message;Reason:530 5.5.1 Authentication Required

Unable to send message;Reason:530 5.5.1 Authentication Required

Hi,

I tried to send this earlier...not sure if this will show as a duplicate...

I have a domain through Wordpress.  I have updated the MXs, pointed to Zoho, etc.
When I try to send an email with the domain as sender (yes, I changed that too) to gmail or aol, I get the above response.
What am I missing?
Thank you,

Kim