In 1818, the postal rule was first introduced in Adams v. Lindsell, when the court had to decide on the date of conclusion of the contract by mail. The postal rule as accepted in the common law legal system: The posting rule applies only to acceptance. Other contractual letters (such as the revocation of the offer) take effect only after the letter has been delivered, as in Stevenson, Jacques & Co v. McLean (1880) 5 QBD 346. As a result, it is possible that a letter of acceptance will be published after the publication of a letter of withdrawal of the offer, but before its delivery, and the acceptance will be complete at the time of publication of the letter of acceptance – the withdrawal of the supplier would be ineffective. In addition to its decision on methods of acceptance, Household Fire and Carriage Accident Insurance Co. v. Grant also states that postal settlement only applies if it is reasonable for an acceptance to be sent by mail. The acceptance must also have been properly stamped, addressed and sent. Many countries have adopted laws based on the UNCITRAL Model Law on Electronic Commerce.
This legislation is often referred to as the Electronic Transactions Act. This legislation deals, among other things, with a standard rule for the time during which e-mails (electronic communications) are sent and received. However, it is wrong to claim that this is a clarification of the postal acceptance rule for electronic communications. There are two schools of thought. Further information on this and other cases, as well as on the postal rule, can be found under the heading „Offer and acceptance“ in the Contract Law section. Following instructions in Household Fire, the courts of Re London and Northern Bank, ex parte Jones , held that a letter of acceptance is considered „properly sent“ only if it is placed in a Royal Mail mailbox or delivered to an employee of the General Post Office who has the right to accept mail for delivery. There are several reasons why the postal rule should apply and why the postal rule should not apply to communication by e-mail over the Internet. The rules on postal contracts (postal regulations) include: „What could be more concretely absurd than the prospect of locomotives running twice as fast as stagecoaches? People could just as easily shoot each other with fireworks. 1 At the beginning of the 19th century, people believed that technological progress had reached its peak, but their predictions were wrong. Locomotives became high-speed trains and postal cars disappeared from the postal system. The mail, which previously took several weeks, arrives after a few days and modern communication systems such as fax, telephone and e-mail have been set up. However, the contract laws of the time and a rule such as the postal rule are still legally binding and, therefore, modern systems and in particular e-mail must be integrated into the legal system.
Critical: Did the postal settlement apply if the bidder required written notice to be accepted? Many jurisdictions call this the mailbox rule, but even in Canada there are disagreements: Waddams calls it in contract law the „mailbox rule; but Fridman, in The Law of Contract, on the „postal acceptance rule.“ Assuming that postal settlement was not applicable, an immediate offer implied that an equally rapid adoption was necessary. On the one hand, the supplier cannot know that the target recipient accepts its offer and is therefore bound by a contract. On the other hand, the provider bears the risk of a communication failure, even if it is not its fault.5 In the modern world, new communication systems have emerged that have had to be integrated into the common law. There have been cases involving all new communication systems such as telephone, fax and telex in the context of the conclusion of the contract. In these cases, such as Entores Ltd. Against Miles Far East Corp.6, the type of communication of the new system was compared to long-established systems and then decided whether the general rule or the postal rule would be applied. The court`s decisions depended on the fact that this system was instantaneous (p. e.g., telephone) or non-instant (e.g., letters).7 In most countries, all modern communication systems such as telephone, telex, fax and website have been classified as instantaneous, and the postal rule does not apply.8 Critical Point Does the postal rule apply if there has been a delay caused by an error? In the United States, the majority rule is that the mailbox rule does not apply to option contracts. By default, an option contract is accepted when the bidder receives acceptance, not when the target recipient sends it.
However, since the California Civil Code applies the mailbox rule to all contracts, California follows the minority rule, according to which the mailbox rule also applies to option contracts.  So far, there are no cases of email. This leads to the question of whether the mail rule applies to email?9 California also applies the mailbox rule to option contracts in the minority of states.