Reconciling two Outlook 2010 mailbox contact lists

I work daily in Outlook 2010 with two mailboxes set up - one for internal communications at work, the other primarily for external customer communications.

I want to have both mailbox contact lists to mirror each other - automatically preferred, but manual (push-button) will still work.

Another solution would be to maintain one contact list and push the list into the other mailbox - but I'm not sure the best way to do that either.

Any assistance or advice will be appreciated.

Thanks.

David W. Lachnicht