A scheduled task runs without an interactive signed-in visitor. Give it the recipient data it needs explicitly; do not assume that a current-user helper will return the person you want to email.
Store the recipient safely
When an authenticated user uses your app, server code can read their verified sign-in email from the request's auth context. Save the address in an appropriately private profile or notification record, together with their notification choices.
The scheduled task can read that record and send the intended message. Keep the record current when the person returns. A stored address does not automatically follow a later account-email change.
Only use this pattern for the messages the recipient expects. The built-in sender's sending limits and policies still apply; see Understanding your email sending limits.
Test before enabling it
Start with your own address and a small test set. Preview can send real emails. Make the task record what it has already sent so a retry does not send the same reminder again.
Publish the task definition when it is ready and verify a real scheduled run. A run finishing is not proof that the recipient received the email. Builder work and billable actions inside the task use credits.