Hi Neil,
sending emails from Innovator normally works very reliable. I didn´t notice any difference in Innovator 11 and 12. I would be the first person to complain about it if it wouldn´t work.
But it´s right now not clear what you currently want to do. Do you want to use Email Message Item from a lifecycle? Or do you want to send an email via Method (you mention a test method)? Do you have a Email server or do you use the temporary folder for testing? There are many details when it comes to emails :-)