There is no reason it could not be binding. But an offer is incomplete - you also need an acceptance, and consideration. This could be an accord and satisfaction, where you and the other party agree to be done with the previous arrangement and create a new agreement. Hope this helps - Elizabeth Powell
Aside from the contract formation concepts already mentioned, your question also focuses on the electronic or e-mail nature of the communication. However, despite the rapid changes in technology over the past 50 years, the law of most states, and federal laws that affect trade and commerce have nearly caught up in some areas.
Not only can electronic expressions be treated as an admissible document, or form part of a contract, or the contract itself, but also electronic signatures are generally recognized as equally binding. The legal focus is on the reliability of the medium or form of communication. The underlying legal requirements of contract formation and legal enforcement are generally the same for electronic media and old-fashioned paper.
The difficulty lies in the fact that many of us treat e-mail as a throwaway communication, often sent without too much careful thought. But, the electronic forms of communication can now carry legal weight just like the form contract signed at the bank.
For further reading: The Electronic Signatures in Global and National Commerce Act (ESIGN, enacted 2000-06-30, 15 U.S.C. ch.96) is a United States federal law passed by the U.S. Congress to facilitate the use of electronic records and signatures in interstate and foreign commerce by ensuring the validity and legal effect of contracts entered into electronically.