Answer: mailbox rule
Step-by-step explanation:
The mailbox rule simply means that acceptance takes effect at the time the offeree sends or delivers the communication via the mode expressly or impliedly authorized by the offeror.
The mailbox rule is typically used in contact law and it applies to offer and its acceptance. When an offer is being made for a particular contact, such offer is seen to be legitimate or has been accepted once it has gotten to the mailbox.