[nikcub]

"contract" in law doesn't mean something written and signed, it is an agreement or implied agreement between two parties. This is a common misconception. The written requirement is only for certain types of binding agreements (land sales, etc.) and varies between jurisdictions. But in most business/service scenarios, oral agreements are just as binding as written agreements.

I was recently involved in a legal dispute where there was no written contract, but the trail of emails and communication was good enough to see judgement in our favor.

[sunchild]

This is 100% correct, but getting it in writing is (almost) always better for enforceability. Also, notice that I never said anything about signatures...

* Since I mentioned that IAAL above, this comment is not legal advice.