Acceptance to terms of agreement over email.

MD of Pvt Ltd Co sent email to an Individual Consultant containing terms of engagement for consulting services. Consultant gave acceptance to this email and started working on company assignment. Consultant insisted MD to provide signed copy of contract. MD replied saying no need for hard copy as digital mail is sufficient.

After offering services for one month co is not making payment to consultant and denying to adhere terms of engagement. As per terms of engagement on termination consultant is entitled to one time payment against contract. Is this valid contract that can be challenged in court of law. Under what law can this be challenged and is this part of cyber-law? What action can consultant take against company and under what section to recover payment as mentioned in terms of engagement letter?