Restrict Access without Creating Users

I believe you are on track; add a parameter to the URL that you can test on page-load.

You could create a GUID and add a table to the database where you store the email address and the GUID; this will make guessing parameters almost impossible. You could also add a timestamp to the table in the database, which you can use to see if the link should still be valid.

Table cells: email, GUID, timestamp

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