https://www.kqed.org/news/11734654/skip-the-slip-california-lawmaker-wants-email-receipts-to-replace-paper-ones
If the default e-receipt bill passes, California would once again become the first in the nation to crack down on another ubiquitous product of modern...
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https://emailreceipts.io/
Automate payment processing and other e-commerce tasks by tracking payments through your email receipts
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https://www.readnotify.com/
Users get free return email notifications, and/or SMS/ICQ instant messages when email they've sent gets opened, and can track their emails reading history
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