The mailbox rule provides that acceptance is effective when it is mailed, with certain exceptions. Which option correctly identifies one of these exceptions?

• A. The offer states otherwise
• B. An irrevocable offer makes acceptance effective only when received
• C. A rejection sent before a mailed acceptance governs
• D. All of the above

Answer: (D)

The mailbox rule says an acceptance is generally effective on mailing, but there are important overrides. If the offer itself states that acceptance is only effective upon receipt, the rule doesn’t apply and binding occurs only when the offeror receives the acceptance. If the offer is irrevocable—think of an option contract or a firm/offered open under the UCC—the acceptance doesn’t bind until it is actually received, ensuring the offeror’s open commitment isn’t undermined by timing. Finally, if a rejection is mailed before the mailed acceptance arrives, the rejection governs because the first substantive communication received controls the formation of the contract. Since each of these is a valid exception, the correct choice recognizes all of them.