Compare a new record to a field in a different table, run task based on result

I have 2 tables, Customers and Requests. Requests a made with a form view with the typical customer details (Name, email, etc). I would like the send an email to new customers. The automation flow would be:

Trigger: New record created in Requests
Action: Check the Email column in Customers to see if there is a match. If the email from the Request is not found, send an email to the Customer to complete the new Customer form.

I have tried with the inbuilt automations. Once the records is created, I can find a record, but I wan’t to run the send email step if there is 0 records returned, but the Automations only allow you to run the next action if something is found.

I also tried to write a script for it. With scripting, once you implement the input variable you can no longer test the script. It also won’t let me return a boolean value. I wan’t nothing to happen if the email is found in Customers, and to only run when a new Request record is created.