Most jurisdictions allow electronic signature now and this would include facsimile transmission. An emailed image has standing as a facsimile transmission.

http://constructionlawnews.com/contract-terms

http://www.wolframlawfirm.com/LawDog...s-applies.aspx

Reciprocity in promissory estoppel;

If you agree to a contract, work is commenced and payment made promissory estoppel is created and future actions are usually governed by the contract's terms if not in conflict with the UCC "Statute of Frauds" (US Law).

*not to be construed as legal advice