When I navigate to the Mail Administration section in the Control Panel, I see the error: "Mail hosting is not enabled for your domain(s). Please enable it in your Control panel to receive emails in Zoho."

But I have enable the domain. The "Domains" section of the Control Panel, shows that everything is set up correctly (except DKIM). I can correctly receive and but not send emails using the domain.

Mail shows as enabled in control panel if I try and disable it it says "operation Not Permitted"

I can recieve mail ok.

But any mail I send bounces back later with:-

Undelivered Mail Returned to Sender