There are no options for that in Q2A currently, but it's a good point so maybe it can be added in future.
In the meantime, one way is to override the qa_send_notification in an override plugin. Here's an example I did a while back to turn off wall posts:
function qa_send_notification($userid, $email, $handle, $subject, $body, $subs, $html = false)
if ( $subject == qa_lang('emails/wall_post_subject') )
return qa_send_notification_base($userid, $email, $handle, $subject, $body, $subs, $html);
You could modify this to check against all the types of email you don't want to send. Look in qa-include/lang/qa-lang-emails.php for the different language keys to check against.