Is delaying informing the customer about the arrival of his transfer for two or three days, due to financial hardship, while delivering the transfer to him immediately upon his arrival and without prior notification, considered a forbidden act?

The relationship between the sender and the recipient of a money order is one of agency, whether the recipient is a branch of the exchange company or its agent. The terms of the contract between the two parties must be adhered to. If the contract stipulates immediate notification, then delay is not permissible. If there is no such condition, then there is no harm.