Newbie Alert!!!

I have two MS Exchange email address set up in Outlook 2016. I want both addresses to use only ONE of the email addresses contact list (not the global one) for (lookup when creating an email address, adding to the one contact list from either email address, etc.).

I have gone into Address Book and made the one Contact List I want use the default, however I am getting email that looks like it has no contact associated with it and I know for sure there is a contact in the one MAIN contact list. The only way to get the inbox to recognize that email as a contact is to add into to the SECOND Exchange account contact list. Suddenly I have two contact list, which I don't want to be the case :-(

Can any of you lovely, newbie tolerant gentle people help me discover how to do so?