tomkotaylor There doesn't appear to be any way we can do it ourselves, you could open a ticket and I am sure Adam would help you fix it. It might be simple config file we can access, or it could be something deeper within orchd. I like your suggestion of the toggle.
Ladylinux I would suggest it's the local smtp server on the host server for the CP. Logs being /var/log/postfix.log? I'd test it for you, but I've since recently set mine as SMTP settings.
Know that the test function actually pipes via enhances own email system I believe, all other system emails come from your local server. Setup a dummy account and test?