Deliver rejected by Zoho

Hi, i´ve configured my Zoho mail account to use it with Gmail and when i try to send an email i get this error:

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the relay smtp.zoho.com by smtp.zoho.com . [165.254.168.48].
The error that the other server returned was:
535 Authentication Failed
(SMTP AUTH failed with the remote server)

What can i do to solve it?

Thank you.