16,000 email list. want a formula to find and remove duplicates.

I have an email list with 16,000+ (A) emails in it (one column). Some are duplicates. I need the formula to find and eliminate the duplicates. I want to save one copy of each duplicate.

A separate but related matter:
I also have another column of emails probably 2000+ (B). I need to find and delete the emails that show up in column A and B.

Thank you for your help.