B2B Email List Cleaning

We have selection of B2B travel agent email lists that has old and new email addresses and a few of the list has incomplete email addresses. We need someone to clean up the list and remove the old email address and remove duplicates and basically tidy it up and create 1 master list. We are looking for somebody who can then scan the list and identify the old dormant email address and incomplete addresses. The total is about 500000