处理电子邮件地址列表的最佳方式

I have got 3 text files (A, B and C), each with several hundred email addresses. I want to merge list A and list B into a single file, ignoring differences in case and white space. Then I want to remove all emails in the new list that are in list C, again ignoring differences in case and white space.I have got 3 text files (A, B and C), each with