Under the mailbox rule, when is an acceptance effective, assuming reasonable means of communication and no contrary language in the offer?

• A. Acceptance is effective only when the offeror receives it.
• B. Acceptance is effective on receipt by the offeror.
• C. Acceptance is effective when the offeree communicates by instant messenger.
• D. Under the mailbox rule, acceptance is effective on dispatch when sent by reasonable means, unless the offer specifies otherwise.

Answer: (D)

The key idea is that the mailbox rule treats acceptance as effective at the moment it is properly dispatched, not when the offeror actually receives it, as long as the method used is reasonable and the offer doesn’t say otherwise. Here, the scenario specifies reasonable means of communication and no contrary language in the offer, so once the offeree sends the acceptance by a reasonable method, the contract is formed at the moment of dispatch. That’s why acceptance is effective on when it is sent, not when it arrives.

The other ideas don’t fit this rule. Acceptance on receipt would contradict the mailbox rule for non-instantaneous communications, and acceptance upon use of an instantaneous method (like instant messaging) reflects a different treatment where effectiveness is typically upon communication or receipt, not upon dispatch.