My partner and I own a retreat center and have one client that returns nearly every month. He never returned a signed contract to us for 2010 and showed up a week early in June when the contract we e-mailed him clearly stated his requested stay was the following weekend. He's e-mailed us back with attached e-mail threads that show he first requested June 18th through the 20th. Two of the subsequent e-mails in his attachment show the requested date of June 25th through the 28th, but not the 18th through the 20th. The contract we sent him towards the end of 2009 clearly shows June 25th through the 28th and he has been to our retreat nearly every month since January of 2010 and paid for those visits. We have never sent him a contract which included the dates of June 18th through the 20th and he doesn't acknowledge even receiving a contract at all. Our question is, Does his payments and arrivals for his other dates in 2010 constitute a legal, binding contract even though he has not returned a signed contract to us?