In the recent case of Nilesh Metha v J Pereira Fernandes S.A.  EWHC 813 (Ch) it was held that, upon sending an email, the automatic addition of an email address after transmission of the email did not, unless there was evidence to show that this was the intention, constitute a signature.
The claimant's solicitors had been emailed a request by a member of the defendant's staff which they had accepted. The defendant subsequently argued that there was no written agreement and the court upheld this argument.
Where emails are intended to form the basis of an agreement, prudent thing to do in such a case would be to include a signature in the body of the email. However, it would also be unwise to place too much reliance on the absence of a signature where seeking to ensure that an email correspondence does not amount to a written agreement, since other factors could come into play. A well drafted email or internet use policy will often identify who in the organisation has authority to enter into contracts that bind the organisation and employees should be made aware of this.