Nice D. Real nice.
I do have a question though.
The "do_action_ref_array" function, specifically in relation to the new wp_mail function.
The way I'm "understanding this", is that the $phpmailer vars being set are passed through this function for additional processing.
Then the additional function can add to that array of vars, and unset one if need be, before returning it back to the wp_mail function, similar to running a filter?
I'm curious because that would be super sweet, as I can drop a quick function in as mu-plugin, unset IsMail, set IsSMTP, pass the connection information, and enable SMTP vice php's mail function.
:D