How to send a payment receipt email
Payment receipts can be sent from the Payment page.
Go to Manage > Financials > Payments and locate the payment. Hover over it and click on the far right blue down arrow. Select the "View" command.
You will see the Edit Payment page. Click on the "More" button in the bottom right, and select the "Send Payment Receipt" command.
You will see a confirmation message. Select "Send Email" to send the message.
Note that you can customize the text of the email by going to Communications > Settings > Notification Templates and editing the appropriate "Payment Receipt" email template.