I’ve also faced same issue, sending the array instead of function parameters doesn’t work.. .
@linuxoid
Just to count one for ‘It Works’, works fine for me.
I always use the smtp method, never the PHP method, always configure the secure smtp method if sending to an email service, or non- secure (port 25) if using postfix.
Have you considered adding postfix as a mail relay on the server? That way Concretecms will deliver the email to postfix very quickly, and postfix can then handle the delivery routing and requeuing as needed.
Using postfix means that email activity is logged in the mail.log file on the server.
I have used this approach across versions from 5.6 through to V9 with total 100% success. Both in my test environments and in production systems.
Will be happy to discuss further if needed.
Martyn