Duplicate emails being received

Greetings all,

I have a database that is used to send out announcements. The agents that send out the emails uses distribution lists that DO NOT reside in the server address book that the announcement database is on. These distribution lists are on another server in another domain and the agent is run manually, that is, by the user sending the announcement. What would be the best way to ensure that the final send to list will only consist of unique names? Write an agent that would pull out all the names in one huge text list/array and do either an @Unique or ArrayUnique? What would the limitations on either method?

My manager's manager is not very happy about getting more than one email for any announcement even though their name is in at least of these distribution lists. Any insight would be greatly appreciated.

Thank you.

Regards - Notes Rookie.