the rule looks good, I have the same rule in my notes.
The only thing could be, that the rule is not matching (for whatever reason). One reason could be, that after the domain part, there are further parameters and therefore the rule doesn't match.
In this case, your rule would look something like this: <taa:rule destination=".*" origin="(.*)@INTERNALDOMAIN.local(.*)">
Have you checked a call with the "locate" tool (Maintenance --> Tools --> Locate) in Expressway and see what happens?
What you also can try is to work with Transforms (Configuration --> Dial plan --> Transforms), as they are GUI based an there for quicker and easier to configure, than CPL rules.
Transforms are applied at the very beginning, when a call hits the Expressway.