Apple Pay - Email Receipts - Assigning Different Email addresses to Credit Cards / Payment Cards ??

Apple Pay doesn’t send receipts, the merchant sends receipts or provides a receipt when the transaction completes.

Are you confusing Apple Pay (tap-to-pay) with your Apple Account?

I's sorry it is inconvenient but please keep in mind that we are just other Apple users in this community forum. All we can do is explain how Apple's process works. If you want to let Apple know that you want a change, then follow Jeff Donald's link to Apple Feedback.

The address information you’re seeing in Wallet & Apple is obtained from your ME contact card in the Apple Contacts app. You can fill in multiple addresses.

The email address is entered directly into the app by tapping Enter New Email Address or Add from Existing Contact.

Apple offers ordering tracking, if that’s what you’re looking for. It needs to be an option the merchant has enabled and you need to enable that option at time of transaction. These aren’t sent by email and require Apple Wallet on your iPhone.

Track orders and purchases in Apple Wallet - Apple Support

I’m still unclear what your reasoning is because merchants don’t send anything via email in almost all cases. If you have an account with the merchant and you log into your account when placing an online order, the merchant uses the email associated with your account if future communication is required.

Apple welcomes your feedback but does not individually reply to your submission.

Feedback - Apple Pay - Apple

Then select the address you want to use for that transaction. Complete the transaction and if anything is sent by merchant, it will be sent to the email selected. Unless you’re logged into a merchant account.

I’m not missing your point. I understand the reasoning. But in practice, I’ve been using Apple Wallet, Apple Pay for nearly 10 years. In all that time, I’ve received maybe 3 or 4 emails from merchants in all that time. Most merchants I have an account and when I log in, they use the email of record for the account.