Data Cleansing - How to keep a list of contacts out of Eloqua contact database?

Does anyone have a solution for keeping a mass list of contacts out of Eloqua? For example, we have a list of 300K contacts that we have removed from Eloqua. We would like to ensure that they do not return to Eloqua by running them against a CDO list but we have found this is not possible because the CDO list of email addresses is no longer attached to the contacts upon deletion of the contacts.