Where (in Foundation) can I find the SharePoint tables/lists containing the users as found under People and Groups?
This can be achieved by performing one of the below steps.
1) Foundation Site - Users- All users here you can see the list.
2) Or in the Database where LMS is installed - Under LMS db there is table dbo.userinfo in that table information is stored . Right click on the table and click on show top 1000 rows.
3) If customer doesnt want to use Current element in Composer to achieve above they can perform the below steps.
a) You can either user the SharePoint User Map element to resolve the Full Name / Login Name of a user based on the e-mail address; if the resolution is successful it is an existing user ; but i think this element only runs on form load so you would need to submit the form to another view to see if the e-mail address is valid or not also this might not work with a repeating table
b) Or The second, much better solution is to make use of the SOAP web services sharepoint offers for user resolution you can import it as an external repeating webservice ; resolve something about the user based on the email address and use that as an indicator to see if it is a real email or not
but this is something completely out of Winshuttle, just happen to know this could work. but it is not a Winshuttle feature