How to receive any value for an entity?

I want the user to be able to ask for the email address of one of their customers without the Rasa NLU having to know the specific customer names. I have a custom action script that will fetch the customer’s email address from our online database (that the user has an account with).

I’ve added 25+ example customer names to train Rasa within various intent examples of how a user might ask for an email address. If the user asks for the email of one of the specified example customer names below (such as “Amy’s Bird Sanctuary”), then my action script successfully receives that entity value. If the user asks for the email of a customer name unknown to Rasa, then my action script receives an EMPTY entity, no value.

How do I configure Rasa to accept ANY value for an entity?

version: "3.0"

- intent: customers_email
  examples: |
    - email address [Amy's Bird Sanctuary]{"entity": "customer_name"}
    - email address for [Barnett Design]{"entity": "customer_name"}
    - mail [Bill's Windsurf Shop]{"entity": "customer_name"}
    - mail for [Cool Cars]{"entity": "customer_name"}
    - mail address [Diego Rodriguez]{"entity": "customer_name"}
    - mail address for [Dukes Basketball Camp]{"entity": "customer_name"}
    - what is email [Dylan Sollfrank]{"entity": "customer_name"}
    - what is email for [Freeman Sporting Goods]{"entity": "customer_name"}
    - what is email address [Geeta Kalapatapu]{"entity": "customer_name"}
    - what is email address for [Gevelber Photography]{"entity": "customer_name"}
    - what is mail [Jeff's Jalopies]{"entity": "customer_name"}
    - what is mail for [John Melton]{"entity": "customer_name"}
    - what is mail address [Kate Whelan]{"entity": "customer_name"}
    - what is mail address for [Kookies by Kathy]{"entity": "customer_name"}
    - tell me email [Mark Cho]{"entity": "customer_name"}
    - tell me email for [Paulsen Medical Supplies]{"entity": "customer_name"}
    - tell me email address [Pye's Cakes]{"entity": "customer_name"}
    - tell me email address for [Rago Travel Agency]{"entity": "customer_name"}
    - tell me mail [Red Rock Diner]{"entity": "customer_name"}
    - tell me mail for [Rondonuwu Fruits and Vegi]{"entity": "customer_name"}
    - tell me mail address [Shara Barnett]{"entity": "customer_name"}
    - tell me mail address for [Sonnenschein Family Store]{"entity": "customer_name"}
    - what's the email [Sushi by Katsuyuki]{"entity": "customer_name"}
    - what's the email for [Travis Waldron]{"entity": "customer_name"}
    - what's the email address for [Weddings by Whitney]{"entity": "customer_name"}
    - what's the mail [Weiskopf Consulting]{"entity": "customer_name"}
    - what's the mail for [customer]{"entity": "customer_name"}
    - what's the mail address [customer]{"entity": "customer_name"}
    - what's the mail address for [customer]{"entity": "customer_name"}
    - tell email [customer]{"entity": "customer_name"}
    - tell email for [customer]{"entity": "customer_name"}
    - tell email address [customer]{"entity": "customer_name"}
    - tell email address for [customer]{"entity": "customer_name"}
    - tell mail [customer]{"entity": "customer_name"}
    - tell mail for [customer]{"entity": "customer_name"}
    - tell mail address [customer]{"entity": "customer_name"}
    - tell mail address for [customer]{"entity": "customer_name"}

Thank you in advance to anyone who can provide some insights…

Just wondering if anyone had any insights or clues that might help me?