Hi Sean,
Survey123 does not do this by default, but depending on how you set up your survey, you could do this.
There are a couple of ways I could envision doing this; both ways require you to have a known list of users:
- Publish the table of users as a feature layer in ArcGIS Online and use a Join to match the submissions to the users.
- Instead of having them submit a new form, pre-create the records they will submit to and provide each user a specialized link that would edit their particular form.
From there, you could easily see which users have not filled out a form and then e-mail them (or have a script do so).
