Multiple email recipients in a workflow

I have a workflow that sends an email based in the value of a field. For some values, i need to send the email to multiple people. The people are outside of my org. Any idea of how to do this? 

Example - Value is Acme
Send email to 3 people

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I do this exact thing.  I use a file cabinet as a lookup with fields Community, SalesPerson1, SalesPerson2, SalesPerson3, SalesPerson4.  Then in the workflow, if a document is submitted for "Community A" it uses the file cabinet to look up the recipients who should be notified for "Community A"