Error_code 554

Error_code 554

  This message was created automatically by mail delivery software.  

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. 

INVALID_ADDRESS, ERROR_CODE :554, ERROR_CODE :5.7.1 <sender-of-o51.zoho.com[135.84.80.216]>: Client host rejected: Access denied 



Please, I need to send email continuosly to two adresses, but I can't.

Please help me.

Thanks