Sample reply to a complaint letter regarding delay in delivery of goods

Dear Sir,

We much regret the delay, and can assure you that we have done our utmost to expedite delivery but the great pressure of orders on these goods have made it impossible for us to delivery as promptly as we wish, and this in spite of the fact that our people are working overtime. We are sorry to have to keep you waiting, as we know you want the goods urgently, and in order to show you that we are anxious to avoid putting you to inconvenience, we have put aside other orders which really should have been got out of hand first.

Our customers are pressing on all sides for immediate delivery, but the demand is unprecedentedly heavy and we are by-no means the only manufacturers of these goods whose resources have been overtaxed. We trust this explanation will convince you of our endeavors to fill your esteemed orders with the best possible despatch, and as, until this recent rush, we have never failed to deliver your orders within the stipulated time we rely upon your leniency in the matter of recent delays. Your esteemed order will at all times receive our most careful and prompt attention.

Thanking you,

Yours faithfully

(Name)