Confirmation / Acknowledgement of purchase order from an existing customer / old client.
Thank you for your recent order, number [ORDER]. We at Company, are alway pleased to have received an order from an old friend.
Your order (Order No.: [xxx]) for [quantity] of [product] is being processed and will be ready for shipment on [DATE]. It will be delivered to your delivery address on [DATE].
[Unfortunately, our stock of [product] has been depleted because of a delay in shipments from our supplier. We have been at great pains to keep up with the demand for this [product]. We have put your order for [product] on back order and hope to have them on their way to you by [DATE].