Commercialese                 modern expressionAdverting to your favor            referring to your letterRe your letter                   thank you for your letterReplying to your letter            I (we) acknowledge your letterThe writer wishes to acknowledge We are in receipt of              we have received your letterWe beg to acknowledge receipt of We have to acknowledgeWe beg to inform you             we are writing to inform youWe respectfully inform youWe beg to thank you             w ...