n00b application design question

[eluser]NogDog[/eluser]
I've only been playing around with CI for a couple of days now, and so far am liking it. I'd like to ask you folks a general design question.

For learning/practice I decided to make a "contact us" email page (no database stuff involved for now). I get the idea that the message submission form would be one view, and the success page another view. I understand how to use the controller to play "traffic cop", do form validation, and such.

What I'm not clear about in this case is whether the "guts" of the email processing -- actually sending the email -- is something that belongs in a controller or in a model. It seems to me it could simply be done as part of the form-handler controller method, calling the necessary methods from the built-in Email class. But I was curious if the experts would do that or put it into a model which was then invoked from the controller.

Thanks.