Talking to my server tech guys and they tell me this:
"We have checked the status of mail service in the server and it is working fine. The problem of 'red' button is isolated to your control panel and it is not affecting any services in the server."
So... I'm back to square one. I can send a preview and a spam test but can not send the actual email even when just a text message.
Any ideas, most appreciated.
Thanks again.