Yes, courts will generally regard emails to be legally binding, and while there may be some exceptions, it is best to presume that a contract will be legally binding to be safe.
Contracts have been in some form or another for as long as humans have existed, and email is only one of the newest modes of communication via which a contract can be created. However, because
email is so new, some people may not think of it as a way to finalise contracts, which can lead to awkward situations if a contract is established unwittingly.
Most people think of contracts as formal agreements put in writing and signed by the parties involved, often with the assistance of lawyers, but the truth is that a contract is simply an agreement between multiple parties concerning the exchange of valuable items, and the physical form of the contract is unimportant.