NOTIFY CUSTOMER THAT ORDER IS DELAYED
I would like to thank you for your order of [PRODUCT (S), ex. 4 Magna flux compressors]. Due to [BRIEFLY STATE REASON, ex. a backlog of orders for this product], however, I regret that your delivery will be delayed. Although I will do my best to expedite your order, we expect shipment to be made on [DATE, ex. Wednesday of next week].
Allow me to apologize for any inconveniences this may have caused you. We look forward to serving you again.