How to set mime mail as default sending method

Hi,
I have set default sending method to "Mime mail" under messaging setting. I am using "Notifications User Autosubscribe 6.x-1.0" module to auto subscribe users. But when a user registered in my site, his sending method is coming as "mail" for blog content type in manage subscription -> administer list.
So my problem is how can I set default sending method to "Mime mail"? so that new subscriptions will have this option automatically.

One more question : Can I send a notification mail to user about "his subscription is successfully cancelled", if he unsubscribed to a content type by clicking on unsubscribing link on notification mails ?

Thanks