In Settings → Receipts, you can add your business name, phone number, website, and anything else you want at the top and bottom of receipts. You can also add a PNG image. It prints in black and white and isn't resized, so you may need to adjust its width in an image editor, and leave some blank space around it so text doesn't overlap it. Use Print test receipt to check your changes.
Email receipts are sent by PostalPoint's cloud service, so you don't need to set up an email account. Under Email Receipts, set the name and email address the receipts appear to come from. Customer replies go to that address. You can also choose the email's color theme and preview it.
Email receipts include your receipt branding text but not the images.