An error occurred while sending mail. The mail server responded: Relaying disallowed as "Flavful.com" <info@flavful.com>. Please check the message and try again.

An error occurred while sending mail. The mail server responded: Relaying disallowed as "Flavful.com" <info@flavful.com>. Please check the message and try again.

I'm receiving the following error when attempting to send an email using SMTP for my account. 

Sending of message failed.
The message could not be sent because the connection to SMTP server smtp.zoho.com was lost in the middle of the transaction. Try again or contact your network administrator.

The settings I'm using are:

Outgoing Server Name: smtp.zoho.com
Port: 465
Security Type: SSL 

Require Authentication: Yes. 

I'm using Postbox as my mail client.