Made possible to create a class which inherits from SmtpMailer

I needed to create an database queue mailer. In order to do that I created a class which inherits from SmtpMailer. I defined my own send() method but I also needed to use methods defined in SmtpMailer. They are private now so I was forced to copy them manually. It would be nice if they were protected so I can use them in SmtpMailer descendants.