localhost setup for using MailServer

I am trying that! I wrote this little function:
public function send_mail($conditions = array()){
$this->load->library('email');
$email=$conditions[where]['email'];
$this->email->from('[email protected]', 'admin at Substantiator.com');
$this->email->to($email);
$this->email->subject('Email Test');
$this->email->message('Testing the email class.');
$this->email->send();
}

Where do I place this function? The code I got is not really sticking to the MVC paradigm. They have a file called userAccount.php which is in Models and has a include 'user.php'; directive at the top. user.php does extend CI_Model. But it is the userAccount.php code which is making the decision to send a password update email. This userAccount.php is not extending the CI_model. I tried putting my send_mail() function in user.php, but when I call it from userAccount.php like this:
send_mail($to,$subject,$mailContent,$headers);

I get an error: Message: Call to undefined function send_mail().

If I take it out of user.php and instead put it directly into userAccount.php, I get

Severity: Parsing Error

Message: syntax error, unexpected 'public' (T_PUBLIC)

So where do I put this CI email functionality?

proof that an old dog can learn new tricks