Hi, in the API you have tie together into the request to create a new subscription v1/billing/subscriptions the subscriber with a specific plan.
You can check this link
We can see that into the request you pass a plan_id and the subscriber object where you can set the email as well:
{ "plan_id": "P-5ML4271244454362WXNWU5NQ", "start_time": "2018-11-01T00:00:00Z", "quantity": "20", "shipping_amount": { "currency_code": "USD", "value": "10.00" }, "subscriber": { "name": { "given_name": "John", "surname": "Doe" }, "email_address": "customer@example.com", "shipping_address": { "name": { "full_name": "John Doe" }, "address": { "address_line_1": "2211 N First Street", "address_li
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