Notify when a new value is entered

One approach would be to add a webservice call to the survey to check the client ID against a list of existing IDs to set an embedded data field that tells you if it is new.  Then use the embedded data field as a condition in the workflow that sends the email.

@TomG The list of existing IDs is sitting in the project’s database...but does that need to be moved (automatically or manually) somewhere else to exist as the reference list for the webservice call, or could it be checked in-place somehow?

I assume when you say “in the project’s database” you mean in previous survey responses. The issue getting them from there is that going through the process of retrieving responses using the Qualtrics API is slow, and you want it to happen immediately. 

I would export them all to a web based database table indexed by id. The web service that checks if an id is new (doesn’t exist) could also add new ids to the database (if it is OK to add them automatically).

you may create a contact list for ID. as someone take the survey you can put an authenticator after the ID was entered, if authentication suceed that mean ID was already exist in contact list and if its fails you can set Embedded data to trigger an email notifcation.

more info on authenticator can be found here.

https://www.qualtrics.com/support/survey-platform/survey-module/survey-flow/advanced-elements/authenticator/authenticator-overview/