What is the Mailbox Rule?

The mailbox rule is a default rule that applies when the offeror does not place specific requirements on the manner of acceptance. Under this rule, the offeree accepts the offer when it is sent to the offeror. This could include dropping it in the mail or sending it with a courier. This may also include providing notice of acceptance via email or other electronic communication (regardless of whether the offeror actually checks or reads the email). As such, if an offer is made to multiple offerees, the first offeree to accept in any manner (including by dropping the acceptance in the mail) has a binding contract.

• Example: You offer to sell me your car for $500. I immediately send you a letter accepting your offer and a $500 check. We have a contract as soon as I drop the letter in the mail.