New answers tagged mail
2
There is no need for a custom table here - you can use the user metadata table and API.
Then create a WP-Cron job to run every 24 hours (or more frequently if you're paranoid). On the callback query users who've registered in the last 7 days using something like:
/*
* Get all users registered after $start and before $end (dates in yyyy-mm-dd format)
* ...
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