Hello @verite-amherst ,
Unless the contacts that are on both lists have to be separated very particularly for the campaign(s), then I'd say just remove all the contacts in one list from the other while preserving both original lists. To go about this:
Copy List A by going into it, select-all the contacts > Actions > Add to list > Create list (I rec naming it something easily recognizable and generic like COPY LIST A)> Add
Go into List B, select-all the contacts > Actions > Remove from list > select COPY LIST A > Remove
Send the email for List A to COPY LIST A, and send the email for List B to it.
If there are certain contacts in both lists that should only receive a specific one of the emails, then you can repeat the first bullet point mentioned above for both lists. From there you'll need to manually remove the applicable contact(s) from the COPY LIST A that absolutely shouldn't receive Email A and remove the contacts from COPY LIST B that shouldn't receive Email B.
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