When a donor opts for a recurring donation, the initial email receipt configured in the campaign editor will be sent to the donor for the first donation.
For subsequent recurring donations, email receipts can be controlled in your Receipt Settings.
To edit this template, click the 'Engage' link in the left navigation panel of your dashboard, then select 'Receipts' to edit your recurring donation receipt, via the 'Recurring Donations' tab.
On the top navigation bar of the Receipts Setting Page, click on the middle tab, 'Recurring Donations' as shown below. You'll see the template to edit subsequent recurring donation receipts.