Sort/Remove Script?

Hey guys, I'm from a Laptop Repair Company. Sorry to barge in here and ask for help randomly, but any suggestions would be greatly greatly appreciated. I post mostly on Actionscript forums to help others using AS3.0, so if you have a question there I could definitely help you lol

I have 2 .xls documents with customer contact information. One has a list of old contacts I need to remove which is about 3k this list contains only email addresses. The other contains the full list of Customers this list is about 11k this contains everything from first/last name to billing and email addresses.

My goal is to double check to see which addresses are just typos and which are non-working.

I will need to go through the list line by line but better to only go through 3000 than 11000. So, I need to somehow remove all of the good addresses from the full list using the bad address list which is only 3k long.

Any suggestions on where to start?

~Rossco