Will the other party know if the courier is not received?

If you send it by courier, the courier company will usually remind the recipient by text message or telephone, so under normal circumstances, the other party knows.

If you send it by ordinary mail, you can pick it up through the mailbox or the doorman. If the recipient can't get it in time, the surface mail company can temporarily store the parcel in the post office or other designated places until the recipient gets it. In this case, the recipient may need to check whether he has received the package, because the surface mail company does not provide real-time reminder service like express delivery.

Of course, if you want to ensure that the recipient receives the package in time, you can choose express delivery service when sending it. Courier companies usually provide real-time logistics information, and you can know whether the package has been signed by the recipient according to this information.