Error 551

Error 551

Hi
I got this message back when sending to my partners email address: veronica@:vghr.net

I manage to send to my gmail address without an issue.

Is this an issue with my zoho setup, or my partners server?

Thanks
Alan
alan.clarke@relocategib.com


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. 

veronica@vghr.net Error, ERROR_CODE :551, ERROR_CODE :This mail server requires authentication before sending mail from a locally hosted domain. Please reconfigure your mail client to authenticate before sending mail.