Restriciting email settings on enewsletter

Hi,

enewsletter is a great plugin, but I'd like to restrict sitewide settings.

Are there wp-config settings, e.g. totally disallow the ability to select php mailer?

More importantly, I don't want my sub site admins to be able to blast massive lists, so I'd like to impose - send by cron only and a limit per hour, .e.g 50/hour

Is any of that possible by hidden config settings / hooks?