Thank you for coming to the Community with your inquiry. Constant Contact made a change last year where you can only have one contact per email address. Click here to learn more information on that change. Before the change, while it was possible for two email addresses under the same contact to be on the same lists, it was a conscious choice on the user to make sure they were there. So when the contacts were split, the secondary email address retained whatever lists it was a part of before the split.
I would compare your Active Contacts number to the number on the list you send to to see if they match. If they do, then you should not have to take any further action. If they don't, then I would select all of your active contacts and add them to the list you send to.
Nick S. Social Media & Content Manager
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