Once a bid has been made, the general rule is that the bidder must communicate its acceptance in order to enter into a binding agreement.  The notification of acceptance must indeed reach a point where the supplier can reasonably be expected to know that he is aware, even if the recipient is guilty, for example. B by not putting enough ink in his fax to print a message that arrives during office hours, the recipient is always bound.  The same applies to all means of communication, whether orally, by telephone, telex, fax or e-mail, with the exception of post. Acceptance by letter is made when the letter is placed in the mailbox. The postal exception is a product of history, and does not exist in most countries.  It exists in English law only as long as it is reasonable to use the contribution for a response (for example.B. not in response to an email), and its operation would not cause obvious inconvenience and nonsense (for example, the letter is lost).  In all cases, it is possible for the parties to the negotiations to define a mandatory method of acceptance.  It is not possible for a supplier to impose an obligation on the bidder to refuse the offer without its agreement.  However, it is clear that people can accept through silence, first by showing by their behavior that they accept. In Brogden/Metropolitan Railway Company, although the Metropolitan Railway Company had never returned a letter from Mr. Brogden forming a long-term supply agreement for Mr.
Brogden`s coal, it had behaved for two years as if it were in force and Mr. Brogden was bound. Second, the supplier may waive the need to notify acceptance, either explicitly or implicitly, as in Carlill v Carbolic Smoke Ball Company.  Here, a sack medicine company advertised its „ball of smoke“ and explained that if a customer found that they did not cure them of the flu after using it twice a day for two weeks, they would receive £100. After the Court of Appeal found that the advertisement was serious enough to be an offer, not just a brothel or an invitation to treatment, the Court of Appeal decided that the accepting party only had to use the smoke balloon as prescribed to obtain the £100. . .