Economics
How the Mailbox Rule Determines Contract Acceptance Timing
Quick fact
Under the mailbox rule, an acceptance is effective the moment it is properly dispatched (e.g., dropped in the mail), not when it is received by the offeror. This means a contract can be formed even if the acceptance is never delivered, as long as it was properly sent.
Why this is interesting
You've just mailed your acceptance to a job offer, but before it arrives, they call to say they've changed their mind. Is there a binding contract? The answer might surprise you.