I'm coming at this from a Research Core, not EX perspective, but assuming the functionality is similiar... we use an automation in our environment that uploads a daily file of new employees to be onboarded. They are all added to the Onboarding list, and then a follow up automation sends the onboarding survey only to the NEW additions to that list.

Hello CarolK , thank you very much for your answer!
Can you share with us a detail of how you created the automation task so that the survey is only sent to new users?
Thank you very much!!

Hi sergiofernandez - we have 2 automations. They are both set up through the XM Directory.
One is an IMPORT automation, set up through the Directory>Automations user interface, which brings in the new recipients and adds them to the list.
Part of the IMPORT automation tells the system we want it to also trigger the second, DISTRIBUTION automation (also set up through the interface)
The default behavior in this case is that only the NEW imported records are sent the distribution, not the ENTIRE list each time.
In combination, the automations tell the system (1) import the records to the master list and (2) send a specific survey to the newly added records X amount of time (usually in hours) after the contacts are added.