Emails not sending

3-13-11: Mom's computer (ACER1), Windows Mail theresa@chcweb.com emails not sending, Windows Security box popping up asking for username and password. Username and password for outgoing server set to same as incoming. Changed to curricula@att.net and att password. Changed incoming port from 25 to 465, and outgoing from 110 to 995, at advice of att tech.