Hi Ewald,
AFAIK, this is not possible with out-of-box. All calls are recorded at the trunk-level and there's no number filtering at the policy level.
A separate trunk makes sense and you can set up your number plan to route to this trunk on certain numbers.
Also, I wonder if its possible to update the conversation while on call where:
1. Trigger on conversation user start
2. Workflow checks data table of numbers to exclude
3. If number exists in data table, update conversation and set recording to 'false'

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Niel Vicente
Technical Lead - DAMAC Properties
Ex-Genesys
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