Yes,
If an agent has no skills, and the calls coming in have skills, the agent cannot take the call. Of course, you need to make sure the calls all have skills assigned to them.
The better option would be to deactivate them in the queue, then they would not get calls but would still be considered a queue member. I haven't tested this, but i'm pretty positive they can still make outbound calls on behalf of the queue.
Hope that helps!
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Kyle Peterson
Athene
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