I can't say anything about, whether John would accept your feature request or not. But for now you can do it using
+ Ability to add your own package items
+ and user create pre/post scripts
Of course you'll need to have some programming skills, or hire somebody to do the job for you. Of course you won't find direct instructions on how to do that with SMTP by those links, I gave you. But with those links you can learn the idea how to implement what you need. That's it.
PM me for a quote, if you're interested, or wait here for a John's answer. Maybe somebody is eager to do it for free.