# Why don't some Apple Pay customers receive card expiration warning emails?

Apple Pay uses [tokenization](https://support.apple.com/en-us/HT203027) to store customer information, which means that Stripe doesn’t have the expiration date for the underlying card. The expiration date used for the [`customer.source.expiring event`](https://stripe.com/docs/api/events/types#event_types-customer.source.expiring) is the one associated with the tokenized card, not the actual customer card. As a result, card expiration warning emails are only sent when [`customer.default_source`](https://docs.stripe.com/api/customers/object#customer_object-default_source) is a [`card`](https://docs.stripe.com/api/cards/object) object and not a [`source`](https://docs.stripe.com/api/sources/object) object.