how can i get my gmail to post to zoho bcc link to zoho customer profile

how can i get my gmail to post to zoho bcc link to zoho customer profile

I tried sending gmails to customers with attachments and add bbb: lzykqs@mails.zoho.com and receive this gmail error message.
 
Delivery to the following recipient failed permanently:

     lzykqs@mails.zoho.com

Technical details of permanent failure:
DNS Error: Domain name not found





I also tried sending the same mails with attachments from Zoho mail and it still doesn't work.

The customer receives their message, but I cannot seem to link up the bcc address correctly. 

I cannot find (or perhaps don't understand) any Zoho documentation that explains how to do this setup.