Our Employee Surveys allow admins to upload CSV files with recipients who may or may not have accounts in their platforms. Those files may have as many columns as the admins want, but only Engaged Index surveys support filtration of the results based on those columns. The only requirement is that those CSV files should contain a column with a unique identifier (e.g., email, id, auth code). The files may contain few other fields too, but none of them are required (e.g., First Name, Last Name, Brand).
Uploading these files happens in User audience section.
Once a file is uploaded, all steps are completed and the survey is saved, the uploaded recipients can start filling the survey. If their emails are provided, they will receive an email, otherwise a custom authentication can be configured and used by the recipients.