Explanation for Delay of Partial Shipment
After some investigation, we believe that we have found the source of the problem that led us to our misunderstanding on [date].
When we received your purchase order for [quantity, product], we were unable to fill the order for immediate delivery due to [explanation for delay in delivery]. Our letter informing you of this delay and requesting your instructions was mailed to youon [date]. We did not receive a reply and proceeded to send a follow-up letter to you on [date].
We have been able to make delivery to you since the [date], but felt that since you had emphasized "for immediate delivery" on your purchase order, we should wait for your authorization before shipping.
I can easily understand why you were so upset with us on [day] if no one made you aware of our correspondence. We have always appreciated having you as a customer and hope that we can continue to provide you with our products in the future.
Very truly yours,