Port protection for email-Yahoo Plus

I checked my Norton settings and found that only ports 25 and 110 are protected for email. I have Yahoo Plus using SSL, so Outlook is set to use ports 995 and 465. But when I try to add these for protection in NIS, I get message that they are "already used by another program." What does thisc mean and what to do? Is that other program actually my Outlook?! Why is NIS protecting 25 and 110, when I am not using these most of the time?