---
title: "Mailbox Rule"
type: Legal Rule
source: https://casebriefly.com/legal-rules/mailbox-rule
---

# Mailbox Rule

Under the mailbox rule, an acceptance is effective upon dispatch (when sent), while rejections and revocations are effective only upon receipt by the other party.

## Definition

The mailbox rule, also known as the dispatch rule or the deposited acceptance rule, provides that an acceptance of an offer is effective at the moment it is dispatched by the offeree, provided it is sent through a reasonable medium of communication. This means that a contract is formed when the acceptance is mailed, not when it is received by the offeror. The rule originated in the English case of Adams v. Lindsell (1818) and has been adopted throughout American contract law.

The mailbox rule creates an asymmetry in contract formation: while acceptances are effective upon dispatch, revocations, rejections, and counteroffers are effective only upon receipt. This means an offeror can be bound to a contract before knowing the acceptance has been sent. The rationale is that once the offeree has dispatched the acceptance, they have done everything within their power to accept and should be able to rely on the existence of the contract.

Several important limitations apply. The rule does not apply if the offer specifically states that acceptance is effective only upon receipt. It does not apply to option contracts, where acceptance must be received. If the offeree sends a rejection first and then an acceptance, the first communication received governs. Under the UCC, the mailbox rule generally applies to contracts for the sale of goods unless the offer provides otherwise. Modern electronic communications have raised questions about the rule's application, with many jurisdictions treating email and electronic acceptances as effective upon dispatch.

## Elements

- A valid offer has been made
- The offeree dispatches an acceptance through a reasonable medium
- The acceptance is properly addressed and dispatched
- The offer does not require receipt for acceptance to be effective
- No prior rejection has been received by the offeror

## Key Case

Adams v. Lindsell, 106 Eng. Rep. 250 (K.B. 1818)

## Landmark Cases

| Name | Citation | Significance |
| --- | --- | --- |
| Adams v. Lindsell | 106 Eng. Rep. 250 (K.B. 1818) | The foundational case establishing that acceptance is effective upon posting, creating the mailbox rule. |
| Morrison v. Thoelke | 155 So. 2d 889 (Fla. Dist. Ct. App. 1963) | Reaffirmed the mailbox rule and held that a mailed acceptance was effective upon dispatch even though the offeree attempted to revoke the acceptance by phone before the letter arrived. |
| Fujimoto v. Rio Grande Pickle Co. | 414 F.2d 648 (5th Cir. 1969) | Applied the mailbox rule in the context of option contracts, discussing the exception that option contract acceptances must be received. |

## Exam Tips

- Create a timeline showing when each communication was sent and received—this is critical for mailbox rule analysis.
- Remember the asymmetry: acceptances effective on dispatch, but revocations and rejections effective on receipt.
- Check whether the offer specifies acceptance is effective only upon receipt—this overrides the mailbox rule.
- Watch for the overtaking acceptance problem: if a rejection is sent first but an acceptance arrives first, the acceptance generally controls.

## Common Mistakes

- Applying the mailbox rule to revocations—revocations are effective upon receipt, not dispatch.
- Forgetting that the offeror can specify that acceptance is effective only upon receipt, overriding the default rule.
- Failing to address the crossing communications scenario where a rejection and acceptance cross in the mail.

## Mnemonic Or Memory Aid

Acceptance is effective when it LEAVES the offeree; revocation is effective when it LANDS on the offeree.

## Related Rules

- mirror-image-rule
- ucc-battle-of-the-forms-2-207
- consideration-doctrine

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Source: [Mailbox Rule — CaseBriefly](https://casebriefly.com/legal-rules/mailbox-rule)