TINN v HOFFMAN
If the offerer requests acceptance through a specific mode, then acceptance can only take place through this mode of communication.
Tinn v Hoffman (1873) 29 LT 271, Exch.Ch
The claimant wrote to defendant to make an inquiry as to how much it would cost to buy 800 tons of iron. The defendant replied, saying that it would cost £3 per ton and requesting the claimant respond "by return".
The court in Tinn v Hoffman held that, as the offer was not actually accepted by return of post, no contract existed.
The offeror can ask for a specific method of acceptance. Honeyman J, on the other hand, stated obiter that a telegram, communication verbally or any other kind of communication that was at least as fast as a letter written by return of post would have sufficed. With this in mind, if an offerer asks for acceptance by post and the offeree sends acceptance through text message, a contract could be held to exist.
The Email further states that if Anna accepts the offer, to confirm the order by letter. The general principle is if the offerer requests acceptance through a specific mode, then acceptance can only take place through this mode of communication. The authority for this is Tinn v Hoffman (1873) 29 LT 271, Exch.Ch. where the offeror asked for acceptance by return of post, the court stated that, due to the offer not being accepted by return of post, the contract therefore did not exist. Anna has accepted the offer by post.