I'm trying to add my Zoho email address to my Gmail account. 

I've gone ahead and attached my domain to zoho, and have tried sending email from it and receiving email to it, and both work fine. 

I'm now trying to connect my account to Gmail, to send email through the Zoho smtp server. 

I use the following info:

SMTP Server: smtp.zoho.com

Username: name@customdomain.com (should i provide actual details here?)

Password: the password i created in zoho for this. 

Toggle on 'Secured connection using SSL' with Port set to 465.

When i do this, I get the following error. 

Authentication failed. Please check your username/password.
Server returned error: "535 Authentication Failed code(535) "

Please advise as to what the problem may be.